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Handbook of 
Meat Processing
Handbook of 
Meat Processing
Fidel Toldrá
EDITOR
A John Wiley & Sons , Inc., Publication
Edition fi rst published 2010
© 2010 Blackwell Publishing
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Library of Congress Cataloging-in-Publication Data
Handbook of meat processing / edited by Fidel Toldrá.
   p. cm.
  Includes bibliographical references and index.
  ISBN 978-0-8138-2182-5 (hardback : alk. paper )  1.  Meat—Handbooks, manuals, etc.  2.  Meat 
industry and trade—Handbooks, manuals, etc.  I.  Toldrá, Fidel. 
 TS1960.H36 2010
 664′.9—dc22
2009037503
A catalog record for this book is available from the U.S. Library of Congress.
Set in 10 on 12 pt  Times by Toppan Best -set Premedia Limited
Printed in Singapore
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The publisher and the author make no representations or warranties with respect to the accuracy or 
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Further, readers should be aware that Internet  Websites listed in this work may have changed or disap-
peared between when this work was written and when it is read.
1 2010
Contents
Preface 
ix
List of Contributors 
xi
About the Editor 
xv
PART I.  Technologies 
3
 1.  Chemistry and Biochemistry of Meat 
5
Elisabeth Huff-Lonergan
 2.   Technological Quality of Meat for Processing 
25
Susan Brewer
 3. Meat 
Decontamination 
43
Panagiotis N. Skandamis, George-John E. Nychas, and John N. Sofos
 4. Aging/Tenderization 
Mechanisms 
87
Brian C. Bowker, Janet S. Eastridge, Ernie W. Paroczay, 
Janice A. Callahan, and Morse B. Solomon
 5. Freezing/Thawing 
105
Christian James and Stephen J. James
 6. Curing 
125
Karl O. Honikel
 7. Emulsifi cation 
143
Irene Allais
 8. Thermal 
Processing 
169
Jane Ann Boles
 9.  Fermentation: Microbiology and Biochemistry 
185
Spiros Paramithiotis, Eleftherios H. Drosinos, John N. Sofos, and 
George-John E. Nychas
10.   Starter Cultures for Meat Fermentation 
199
Pier Sandro Cocconcelli and Cecilia Fontana
11. Drying 
219
Endre Zukál and Kálmán Incze
v
vi    Contents
12.  Smoking  
231
Zdzisław E. Sikorski and Edward Kol
´akowski
13. Meat 
Packaging 
247
Maurice G. O’Sullivan and Joseph P. Kerry
14.   Novel  Technologies for Microbial Spoilage Prevention  
263
Oleksandr Tokarskyy and Douglas L. Marshall
15.   Plant Cleaning and Sanitation 
287
Stefania Quintavalla
PART II.  Products 
299
16. Cooked 
Ham 
301
Fidel Toldrá, Leticia Mora, and Mónica Flores
17. Cooked 
Sausages 
313
Eero Puolanne
18.  Bacon  
327
Peter R. Sheard
19.  Canned Products and Pâté 
337
Isabel Guerrero Legarreta
20. Dry-Cured 
Ham 
351
Fidel Toldrá and M. Concepción Aristoy
21.  Mold -Ripened 
Sausages 
363
Kálmán Incze
22.  Semidry and Dry Fermented Sausages 
379
Graciela Vignolo, Cecilia Fontana, and Silvina Fadda
23. Restructured 
Whole -Tissue 
Meats 
399
Mustafa M. Farouk
24.   Functional Meat Products 
423
Keizo Arihara and Motoko Ohata
PART III.  Controls 
441
25.   Physical Sensors for Quality Control during Processing 
443
Marta Castro -Giráldez, Pedro José Fito, Fidel Toldrá, and Pedro Fito
26.  Sensory Evaluation of Meat Products 
457
Geoffrey R. Nute
27.  Detection of Chemical Hazards  
469
Milagro Reig and Fidel Toldrá
28.  Microbial Hazards in Foods : Food-Borne Infections and Intoxications 
481
Daniel Y. C. Fung
Contents    vii
29.   Assessment of Genetically Modifi ed Organisms (GMO) in Meat Products 
by PCR 
501
Marta Hernández, Alejandro Ferrando, and David Rodríguez-Lázaro
30.   HACCP : Hazard   Analysis Critical Control Point 
519
Maria Jo ã o Fraqueza and António Salvador Barreto
31. Quality 
Assurance 
547
Friedrich-Karl Lücke
Index 
561
 Preface 
      For  centuries,  meat  and  its  derived  products 
worldwide meat products such as cooked 
have constituted some of the most important  
ham and sausages, bacon, canned products 
foods consumed in many countries around  
and  p â t é ,  dry - cured  ham,  mold - ripened  sau-
the world. Despite this important role , there  
sages, semidry and dry fermented sausages, 
are few books dealing with meat and its 
restructured meats, and functional meat prod -
processing technologies. This book provides 
ucts. The third part presents effi cient strate-
the reader with an extensive description of 
gies to control the sensory and safety quality 
meat processing, giving the latest advances 
of meat and meat products, including physi-
in technologies, manufacturing processes , 
cal sensors, sensory evaluation, chemical 
and tools for the effective control of safety 
and microbial hazards, detection of GMOs, 
and quality during processing. 
HACCP, and quality assurance. 
 To achieve this goal, the book contains 31 
 The chapters have been written by distin-
chapters distributed in three parts. The fi rst 
guished international experts from fi fteen 
part deals with the description of meat chem -
countries. The editor wishes to thank all the 
istry, its quality for further processing, 
contributors for their hard work and for 
and the main technologies used in meat 
sharing their valuable experience , as well as 
processing, such as decontamination, aging, 
to thank the production team at Wiley 
freezing, curing, emulsifi cation, thermal pro-
 Blackwell. I also want to express my appre-
cessing, fermentation, starter cultures, drying, 
ciation to Ms. Susan Engelken for her kind 
smoking, packaging, novel technologies, 
support and coordination of this book. 
and cleaning. The second part describes the 
manufacture and main characteristics of 
   Fidel  Toldr á  
 
ix
 Contributors 
 Irene Allais 
 Susan Brewer 
 Cemagref, UMR Genial, Equipe  Automat  
 Food Science and Human Nutrition, 
 &  Qualite Alimentaire, 24 Av Landais, 
University of Illinois, USA. 
F - 63172  Aubiere  1,   France . 
 E - mail:   msbrewer@illinois.edu  
 E - mail:   irene.allais@cemagref.fr  
 Janice A. Callahan 
 Keizo Arihara 
 Food  Technology and Safety Laboratory , 
  Department of  Animal Science, Kitasato 
Bldg 201, BARC -  East , Beltsville, Maryland 
University,  Towada - shi,  Aomori  034 - 8628, 
20705, USA. 
Japan . 
 E - mail:   Janice.callahan@ars.usda.gov  
 E - mail:   arihara@vmas.kitasato - u.ac.jp  
 Marta Castro - Gir á ldez 
 M. Concepci ó n Aristoy 
 Institute of Food Engineering for 
 Department of Food Science, Instituto de 
Development ,  Universidad  Polit é cnica  de 
Agroqu í mica   y  Tecnolog í a  de  Alimentos 
Valencia , Camino de Vera s/n, 46022 
(CSIC), PO Box 73, 46100 Burjassot 
Valencia, Spain . 
(Valencia), Spain. 
 E - mail:   mcaristoy@iata.csic.es  
 Pier Sandro Cocconcelli 
 Istituto di Microbiologia, Centro Ricerche 
 Ant ó nio Salvador Barreto 
Biotecnologiche, Universit à  Cattolica del 
 Faculdade  de  Medicina  Veterin á ria, 
Sacro Cuore, Piacenza - Cremona, Italy . 
DPASA, TULisbon, Av. da Universidade 
 E - mail:   pier.cocconcelli@unicatt.it  
Tecnica, Polo Universit á rio, Alto da Ajuda, 
1300 - 477  Lisboa,  Portugal. 
 Eleftherios H. Drosinos 
 Laboratory of Food Quality Control and 
 Jane Ann Boles 
Hygiene , Department of Food Science and 
 Animal and Range Sciences , 119 
Technology, Agricultural University of 
Linfi eld Hall, Bozeman, Montana 
Athens, Iera Odos 75, Votanikos, 11855 
59717, USA. 
Athens, Greece . 
 E - mail:   jboles@montana.edu  
 E - mail:   ehd@aua.gr  
 Brian C. Bowker 
 Janet S. Eastridge 
 Food Technology and Safety Laboratory, 
 Food Technology and Safety Laboratory, 
Bldg 201, BARC - East, Beltsville, 
Bldg 201, BARC - East, Beltsville, Maryland 
Maryland 20705, USA. 
20705, USA. 
 E - mail:   brian.bowker@ars.usda.gov  
 E - mail:   janet.eastridge@ars.usda.gov  
xi
xii    Contributors
 Silvina Fadda 
 Maria Jo ã o Fraqueza 
 Centro de Referencia para Lactobacilos 
 Faculdade  de  Medicina  Veterin á ria, 
(CERELA), CONICET., Chacabuco 145, 
DPASA, TULisbon, Av. da Universidade 
T4000ILC  Tucum á n,   Argentina . 
Tecnica, Polo Universit á rio, Alto da Ajuda, 
 E - mail:   fadda@cerela.org.ar  
1300 - 477  Lisboa,  Portugal. 
 E - mail:   mjoaofraqueza@fmv.utl.pt  
 Mustafa M. Farouk 
 AgResearch MIRINZ, Ruakura Research 
 Daniel Y. C. Fung 
Centre , East Street, Private Bag 3123, 
 Department of Animal Sciences and 
Hamilton 3240, New Zealand . 
Industry, 207 Call Hall, Kansas State 
 E - mail:   mustafa.farouk@agresearch.co.nz  
University, Manhattan, Kansas 66506, 
USA. 
 E - mail:   dfung@ksu.edu  
 Alejandro Ferrando 
 Departamento  de  Bioqu í mica  y  Biolog í a 
Molecular, Facultad de Biolog í a, 
 Isabel Guerrero Legarreta 
Universidad de Valencia, Dr Moliner, 50, 
 Departamento  de  Biotecnolog í a, 
Burjassot, 46100 Valencia, Spain. 
Universidad Aut ó noma,  Metropolitana, 
Unidad Iztapalapa, San Rafael Atlixco 186, 
Del. Iztapalapa, Apartado Postal 55 - 535, 
 Pedro Fito 
C.P. 092340, Mexico City. 
 Institute of Food Engineering for 
 E - mail:   meat@xanum.uam.mx  
Development,  Universidad  Polit é cnica  de 
Valencia, Camino de Vera s/n, 46022 
Valencia, Spain. 
 Marta Hern á ndez 
 E - mail:   pfi to@tal.upv.es  
 Laboratory of Molecular Biology and 
Microbiology,  Instituto  Tecnol ó gico 
Agrario de Castilla y Le ó n (ITACyL), Ctra. 
 Pedro Jos é  Fito 
Burgos km.119, Finca Zamadue ñ as, 47071 
 Institute of Food Engineering for 
Valladolid, Spain. 
Development,  Universidad  Polit é cnica  de 
Valencia, Camino de Vera s/n, 46022 
Valencia, Spain. 
 Karl O. Honikel 
 E - mail:   pjfi to@tal.upv.es  
 Max  Rubner - Institut,  Arbeitsgruppe 
Analytik, Kulmbach, Germany . 
 E - mail:   karl - otto.honikel@t - online.de  
 M ó nica Flores 
 Department of Food Science, Instituto de 
Agroqu í mica  y  Tecnolog í a  de  Alimentos 
 Elisabeth Huff - Lonergan 
(CSIC), PO Box 73, 46100 Burjassot, 
  Muscle Biology, Department of Animal 
Valencia, Spain. 
Science, Iowa State University, 2275 Kildee 
 E - mail:   mfl ores@iata.csic.es  
Hall, Ames, IA 50011 USA. E - mail: 
 elonerga@iastate.edu  
 Cecilia Fontana 
 Centro de Referencia para Lactobacilos 
 K á lm á n Incze 
(CERELA), CONICET., Chacabuco 145, 
  Hungarian Meat Research Institute, 1097 
T4000ILC  Tucum á n,  Argentina. 
Budapest, Gubacsi  ú t 6/b, Hungary . 
 E - mail:   cecilia.fontana@unicatt.it  
 E - mail:   ohki@interware.hu  
Contributors    xiii
 Christian James 
 Douglas L. Marshall 
 Food Refrigeration and Process Engineering 
 College of Natural and Health Sciences, 
Research Centre (FRPERC), The Grimsby 
University of Northern Colorado, 
Institute of Further and Higher  
Campus Box 134, Greeley, Colorado 
Education(GIFHE), HSI Building, Origin  
80639 USA. 
Way, Europarc, Grimsby, North East 
 E - mail:   douglas.marshall@unco.edu  
Lincolnshire, DN37 9TZ UK. 
 E - mail:   JamesC@grimsby.ac.uk  
 Leticia Mora 
 Department of Food Science, Instituto de 
Agroqu í mica  y  Tecnolog í a  de  Alimentos 
 Stephen J. James 
(CSIC), PO Box 73, 46100 Burjassot 
 Food Refrigeration and Process Engineering 
Valencia, Spain. 
Research Centre (FRPERC), The Grimsby 
 E - mail:   lemoso@iata.csic.es  
Institute of Further and Higher 
Education(GIFHE), HSI Building, Origin 
Way, Europarc, Grimsby, North East 
 Geoffrey R. Nute 
Lincolnshire, DN37 9TZ UK. 
 University of Bristol , School of Clinical 
 E - mail:   jamess@grimsby.ac.uk  
Veterinary Science, Division of Farm  
Animal Science, Bristol BS40 5DU, Avon, 
England . 
 Joseph P. Kerry 
 E - mail:   Geoff.Nute@bristol.ac.uk  
 Department of Food and Nutritional 
Sciences, University College Cork, Ireland. 
 George - John E. Nychas 
 E - mail:   Joe.Kerry@ucc.ie  
 Laboratory of Food Microbiology  &  
Biotechnology, Department of Food 
 Edward Ko ł akowski 
Science   &   Technology,  Agricultural 
University of Athens, Iera Odos 75, Athens 
 Department of Food Science and 
11855, Greece. 
Technology, Agricultural University of 
 E - mail:   gjn@aua.gr  
Szczecin, Papie  a Paw ł a VI St. 3, 71 - 459 
Szczecin, Poland. 
 E - mail:   ekolakowski@tz.ar.szczecin.pl  
 Motoko Ohata 
 Department of Animal Science, Kitasato 
University,  Towada - shi,  Aomori  034 - 8628, 
 Catherine M. Logue 
Japan. 
 Department of Veterinary and 
Microbiological Sciences, North Dakota 
 Maurice G. O ’ Sullivan 
State University, 1523 Centennial Blvd, 
 Department of Food and Nutritional 
130A Van Es Hall, Fargo, North Dakota 
Sciences, University College Cork, Ireland. 
58105, USA. 
 E - mail:   maurice.osullivan@ucc.ie  
 E - mail:   Catherine.Logue@ndsu.edu  
 Spiros Paramithiotis 
 Friedrich - Karl L ü cke 
 Laboratory of Food Quality Control and 
 Hochschule Fulda (University of Applied 
Hygiene, Department of Food Science and 
Sciences), P.O. Box 2254, 36012 Fulda, 
Technology, Agricultural University of 
Germany. 
Athens, Iera Odos 75, 11855 Athens, 
 E - mail:   friedrich - karl.luecke@t - online.de  
Greece. 
xiv    Contributors
 Ernie W. Paroczay 
 Panagiotis N. Skandamis 
 Food Technology and Safety Laboratory, 
 Laboratory of Food Quality Control and 
Bldg 201, BARC - East, Beltsville, 
Hygiene, Department of Food Science and 
Maryland 20705, USA. 
Technology, Agricultural University of 
 E - mail:   ernie.paroczay@ars.usda.gov  
Athens, Iera Odos 75, Votanikos, 11855 
Athens, Greece. 
 Eero Puolanne 
 Department of Food Technology, Viikki 
 John N. Sofos 
EE, P.O. Box 66, 00014 Helsinki, Finland. 
 Colorado State University, Fort Collins, 
 E - mail:   Eero.Puolanne@helsinki.fi   
Colorado 80523, USA. 
 E - mail:   John.Sofos@ColoState.EDU  
 Stefania Quintavalla 
 Department of Microbiology, SSICA, V.le 
Tanara 31/A, 43100, Parma, Italy. 
 Morse B. Solomon 
 E - mail  address:   stefania.quintavalla@ssica.it  
 Food Technology and Safety Laboratory, 
Bldg 201, BARC - East, Beltsville, Maryland 
 Milagro Reig 
20705, USA. 
 Institute of Food Engineering for 
 E - mail:   Morse.Solomon@ARS.USDA.GOV  
Development,  Universidad  Polit é cnica  de 
Valencia, Camino de Vera s/n, 46022 
 Oleksandr Tokarskyy 
Valencia, Spain. 
 Department of Food Science, Nutrition, and 
 E - mail:   mareirie@doctor.upv.es  
Health Promotion, Mississippi State 
University, Box 9805, Mississippi State 
 David Rodr í guez - L á zaro 
University, Mississippi 39762 USA. 
 Food Safety and Technology Group, 
Instituto Tecnol ó gico Agrario de Castilla y 
 Fidel Toldr á  
Le ó n (ITACyL), Ctra. Burgos km.119, 
 Department of Food Science, Instituto de 
Finca  Zamadue ñ as,  47071  Valladolid, 
Agroqu í mica  y  Tecnolog í a  de  Alimentos 
Spain. 
(CSIC), PO Box 73, 46100 Burjassot, 
 E - mail:   ita - rodlazda@itacyl.es  
Valencia, Spain. 
 E - mail:   ftoldra@iata.csic.es  
 Peter R. Sheard 
 Division of Farm Animal Science, School 
of Clinical Veterinary Science, University 
 Graciela Vignolo 
of Bristol, Bristol BS40 5DU, Avon, UK. 
 Centro de Referencia para Lactobacilos 
 E - mail:   Peter.Sheard@bristol.ac.uk  
(CERELA), CONICET., Chacabuco 145, 
T4000ILC  Tucum á n,  Argentina. 
 Zdzis ł aw E. Sikorski 
 E - mail:   vignolo@cerela.org.ar  
 Department of Food Chemistry, Gda n´ sk 
University of Technology 
 Endre Zuk á l 
 E - mail:   sikorski@chem.pg.gda.pl   OR 
 Hungarian Meat Research Institute, 
 zdzsikor@pg.gda.pl  
Budapest 1097, Gubacsi  ú t 6/b, Hungary. 
 
 About the Editor 
      Fidel  Toldr á ,  Ph.D.,  is  a  research   professor   at 
years , including  
Handbook of Muscle 
the Department of Food Science, Instituto de 
Foods Analysis  and  Handbook of Processed 
Agroqu í mica  y  Tecnolog í a  de  Alimentos 
Meats and Poultry  Analysis 
 (2009),  
Meat 
(CSIC), and serves as European editor of 
Biotechnology 
 and  
Safety of Meat and 
  Trends in Food Science  &  Technology ,  editor 
Processed Meat  (2008, 2009),  Handbook of 
in chief of   Current   Nutrition   &   Food  Science, 
Food Product Manufacturing  
(2007), 
and as section editor of the   Journal of Muscle 
 Advances in Food Diagnostics , and  Handbook 
Foods 
. He is also serving on the editorial 
of Fermented Meat and Poultry  (2007, 2008). 
board of the journals  Food Chemistry ,   Meat 
Professor Toldr á  also wrote the book  Dry -
Science ,    Open Nutrition Journal ,   Food 
 Cured Meat Products   (2002). 
Analytical Methods ,   Open Enzyme Inhibition 
 Professor Toldr á  was awarded the 2002 
Journal  and  Journal of Food and Nutrition 
International Prize for meat science and tech -
Research . He is a member of the European 
nology by the International Meat Secretariat 
Food Safety Authority panel on fl avorings, 
and was elected in 2008 as Fellow of the 
enzymes, processing aids, and materials in 
International Academy of Food Science  
& 
 
contact with foods. 
Technology (IAFOST) and in 2009 as 
 
Professor Toldr 
á 
 has acted as editor or 
Fellow of the Institute of Food Technologists 
associate editor of several books in recent  
(IFT).      
xv
Handbook of 
Meat Processing
Part I
 Technologies 
Chapter 1
 Chemistry and Biochemistry of Meat  
 Elisabeth   Huff - Lonergan  
 
  Introduction  
content is 75% of the weight of the muscle; 
however , can vary , particularly in postmor-
 Muscle cells are among the most highly orga -
tem muscle (range of 65 – 80%).  Within the 
nized cells in the animal body and perform a 
muscle, it is the primary component of extra -
varied array of mechanical functions . They 
cellular fl uid. Within the muscle cell, water 
are required for the movement of limbs, 
is the primary component of sarcoplasmic  
for locomotion and other gross movements, 
(cytoplasmic) fl uid. It is important in thermo -
and they must also perform fi ner  tasks 
regulation ; as a medium for many cellular 
such as maintaining balance and coordina-
processes; and for transport of nutrients 
tion. Muscle movement and metabolism  
within the cell, between cells, and between 
are associated with other diverse functions 
the muscle and the vascular system.  
such as aiding in movement of blood and 
 The second largest component of muscle 
lymph and also in maintaining body tempera -
is protein (U.S. Department of  Agriculture  
ture. All of these functions are dependent  
 2008 ). Protein makes up an average of 18.5% 
on cellular metabolism and the ability of the 
of the weight of the muscle, though that 
cell to maintain energy supplies. Few cells 
fi gure can range from 16 to 22%. Proteins 
are required to generate as much force and 
serve myriad functions and are the primary 
undergo as dramatic shifts in rate of metabo-
solid component in muscle. The functions of 
lism as muscle cells. The ability of living  
proteins are quite varied. Muscle proteins are 
skeletal muscle to undergo relatively large 
involved in maintaining the structure and 
intracellular changes also infl uences  its 
organization of the muscle and muscle cells 
response to the drastic alterations that occur  
(the role of highly insoluble stromal pro-
during the fi rst few hours following exsan-
teins). They are also important in the contrac-
guination. Thus the organization, structure, 
tile process. These proteins primarily are 
and metabolism of the muscle are key to its 
associated with the contractile organelles, the 
function and to the maintenance of its integ -
myofi bril, and are thus termed myofi brillar 
rity both during contraction and during the 
proteins. In general, the myofi brillar proteins 
early postmortem period . Ultimately, these 
are not soluble at low ionic strengths found  
postmortem changes will infl uence the suit -
in skeletal muscle (ionic strength  ≤ 0.15),  but 
ability of meat for further processing.  
can be solubilized at higher ionic strengths 
( ≥ 0.3). This class of proteins includes both 
the proteins directly involved in movement 
 Muscle Composition  
(contractile proteins) and proteins that regu-
 
The largest constituent of muscle is water 
late the interactions between the contractile 
(Table  1.1 ; U.S. Department of Agriculture 
proteins (regulatory proteins). There are also 
 
2008 
). In living tissue, the average water 
many soluble proteins (sarcoplasmic pro-
5
6    Chapter 1
 Table 1.1.    Composition of Mammalian Muscle 
complex lipid found in muscle. In this class 
of lipids, one of the hydroxyl groups of glyc-
   Component  
   %  of  Muscle  Weight  
erol is esterifi ed to a phosphate group, while  
  Water  
  75%  (65 – 80%)  
  Protein  
  18.5%  (16 – 22%)  
the other constituents are fatty acids. The 
  Lipid  
  3%  (1 – 13%)  
fatty acids associated with phospholipids are 
  Carbohydrate  
  1%  (0.5 – 1.5%)  
typically unsaturated. Phospholipids in skel -
  Non - Protein  Nitrogenous 
  1.7%  (1 – 2%)  
Substances  
etal muscle are commonly associated with 
  Other  Non - Protein 
  0.85%  (0.5 – 1%)  
membranes. The relative high degree of 
Substances (minerals, 
unsaturation of the fatty acids associated with 
vitamins, etc.)  
the phospholipids is a contributing factor to 
  Numbers in parentheses indicate the average range of 
the fl uidity of the cell membranes. 
that  component.    (U.S.  Department  of  Agriculture,   2008 ) 
 Carbohydrates make up a relatively small 
percentage of muscle tissue, making up about 
1% of the total muscle weight (range of 0.5 –
teins) that include proteins involved in cel-
 1.5%). The carbohydrate that makes up the 
lular signaling processes and enzymes  largest percentage is glycogen. Other carbo-
important in metabolism and protein degra-
hydrates include glucose, intermediates of 
dation/cellular remodeling. 
glycogen metabolism, and other mono  -  and 
 The lipid content of the muscle can vary 
disaccharides. Glycosoaminoglycans are also 
greatly due to many factors, including animal 
found in muscle and are associated with the 
age, nutritional level of the animal, and 
connective tissue. 
muscle type. It is important to note that the 
 There are numerous non - protein nitroge-
lipid content varies inversely with the water 
nous compounds in skeletal muscle. They 
content (Callow  1948 ). Some lipid is stored  
include substances such as creatine and cre-
inside the muscle cell; however, within a 
atine phosphate, nucleotides (ATP, ADP), 
muscle, the bulk of the lipid is found between 
free amino acids, peptides (anserine, carno-
muscle bundles (groupings of muscle cells). 
sine), and other non - protein substances.  
Average lipid content of skeletal muscle is 
about 3% of the muscle weight, but the range 
 Muscle Structure 
can be as much as 1 – 13% (U.S. Department 
of Agriculture  
2008 
). In skeletal muscle, 
 Skeletal muscle has a very complex organi-
lipid plays roles in energy storage , membrane 
zation, in part to allow muscle to effi ciently 
structure, and in various other processes in 
transmit force originating in the myofi brils to 
the organ, including immune responses and 
the entire muscle and ultimately, to the limb 
cellular recognition pathways. 
or structure that is moved. A relatively thick 
 
The two major types of lipid found in 
sheath of connective tissue, the epimysium, 
skeletal muscle are triglycerides and phos-
encloses the entire muscle. In most muscles, 
pholipids. Triglycerides make up the greatest 
the epimysium is continuous , with tendons 
proportion of lipid associated with muscle. 
that link muscles to bones. The muscle is 
Triglycerides (triacylglycerides) consist of a 
subdivided into bundles or groupings of 
glycerol molecule in which the hydroxyl 
muscle cells. These bundles (also known as 
groups are esterifi ed with three fatty acids. 
fasciculi) are surrounded by another sheath 
The melting point and the iodine number of 
of connective tissue, the perimysium. A  thin  
lipid that is associated with the muscle is 
layer of connective tissue, the endomysium, 
determined by the chain length and the degree 
surrounds the muscle cells themselves. The 
of saturation of the fatty acids. Phospholipids 
endomysium lies above the muscle cell mem-
(phosphoglycerides) are another type of 
brane (sarcolemma) and consists of a base-
Chemistry and Biochemistry of Meat    7
ment membrane that is associated with an 
basis , they make up approximately 10 – 12% 
outer layer (reticular layer) that is surrounded 
of the total weight of fresh skeletal muscle. 
by a layer of fi ne collagen fi brils imbedded 
Therefore , they are very important in meat 
in a matrix (Bailey and Light  1989 ). 
chemistry and in determining the functional-
 
Skeletal muscles are highly diverse, in 
ity of meat proteins. 
part because of the diversity of actions they 
 Myofi brils are the contractile  “ machinery ”  
are asked to perform. Much of this diversity 
of the cell and, like the cells where they 
occurs not only at the gross level, but also at 
reside, are very highly organized. When 
the muscle cell (fi ber) level. First , not only 
examining a myofi bril, one of the fi rst obser-
do muscles vary in size , they can also vary 
vations that can be made is that the cylindri-
in the number of cells. For example, the 
cal organelle is made up of repeating units . 
muscle that is responsible for adjusting the 
These repeating units are known as sarco-
tension of the eardrum (tensor tympani) 
meres. Contained in each sarcomere are all 
has only a few hundred muscle cells, while 
the structural elements needed to perform the 
the medial gastrocnemius (used in humans  
physical act of contraction at the molecular 
for walking) has over a million muscle cells 
level. Current proteomic analysis estimates 
(Feinstein et al.  
1955 
). Not only does the 
that over 65 proteins make up the structure 
number of cells infl uence muscle function 
of the sarcomere (Fraterman et al.  
2007 
). 
and ultimately, meat quality, but also the 
Given that the sarcomere is the most basic  
structure of the muscle cells themselves 
unit of the cell and that the number quoted in 
has a profound effect on the function of 
this analysis did not take into account the 
living muscle and on the functionality of 
multiple isoforms of the proteins, this number 
meat. 
is quite high. Many of the proteins interact 
 
Muscle cells are striated, meaning that 
with each other in a highly coordinated 
when viewed under a polarized light micro-
fashion, and some of the interactions are just 
scope, distinct banding patterns or striations 
now being discovered. 
are observed . This appearance is due to spe-
 The structure of the sarcomere is respon-
cialized organelles, myofi 
brils, found in 
sible for the striated appearance of the muscle 
muscle cells. The myofi brils have a striated, 
cell. The striations arise from the alternating, 
or banded, appearance because different  
protein dense A - bands and less dense I - bands 
regions have different refractive properties. 
within the myofi bril. Bisecting the I - bands 
The light bands have a consistent index of 
are dark lines known as Z - lines. The structure 
refraction (isotropic). Therefore, these bands 
between two Z - lines is the sarcomere. In a 
are called I - bands in reference to this isotro-
relaxed muscle cell, the distance between 
pic property. The dark band appears dark 
two Z - lines (and thus the length of the sarco-
because it is anisotropic and is thus called the 
mere) is approximately 2.2 
 
μ m.  A   single  
A - band. 
myofi bril is made up of a large number of 
 The  myofi brils are abundant in skeletal 
sarcomeres in series. The length of the myo-
muscle cells, making up nearly 80 – 90% of 
fi bril and also the muscle cell is dependent 
the volume of the cell. Myofi brillar proteins 
on the number of sarcomeres. For example, 
are relatively insoluble at physiological ionic 
the semitendinosus, a long muscle, has been 
strength, requiring an ionic strength greater  
estimated to have somewhere in the neigh-
than 0.3 to be extracted from muscle. For this 
borhood of 5.8    ×  10 4  to 6.6    ×  10 4   sarcomeres 
reason , they are often referred to as  “  salt  -
per muscle fi ber, while the soleus has been 
 soluble ”   proteins.  Myofi brillar proteins make 
estimated to have approximately 1.4    ×   10 4 
up approximately 50 – 60% of the total extract-
(Wickiewicz et al.  
1983 
). Adjacent myofi -
able muscle proteins. On a whole muscle 
brils are attached to each other at the Z - line 
8    Chapter 1
by proteinacious fi laments, known as inter -
each) and two sets of light chains (14,000 –
mediate fi laments. Outermost myofi brils are 
 20,000 daltons). One of the light chains is 
attached to the cell membrane (sarcolemma) 
required for enzymatic activity , and the other 
by intermediate fi laments that interact not 
has regulatory functions. 
only with the Z - line, but also with structures  
 Actin is the second - most abundant protein 
at the sarcolemma known as costameres 
in the myofi bril, accounting for approxi-
(Robson  et  al.   2004 ). 
mately 20% of the total protein in the myo-
 Myofi brils are made up of many myofi la-
fi bril. Actin is a globular protein (G - actin) 
ments, of which there are two major types, 
that polymerizes to form fi laments  (F - actin). 
classifi ed as thick and thin fi laments. There 
G - actin has a molecular weight of approxi-
is also a third fi lament system composed pri-
mately 42,000. There are approximately 
marily of the protein titin ( Wang et al.  1979 ; 
400 actin molecules per thin fi lament. Thus 
Wang  
1984 
; Wang et al.  
1984 
; Wang and 
the molecular weight of each thin fi lament 
Wright  1988 ; Wang et al.  1991 ; Ma et al. 
is approximately 1.7 
  
 
×   10 7   (Squire   1981 ). 
 2006 ;). With respect to contraction and rigor 
The thin fi laments (F 
- 
actin polymers) are 
development in postmortem muscle, it is the 
1     μ 
m in length and are anchored in the 
interdigitating thick and thin fi laments  that 
Z - line. 
supply the  “ machinery ”  needed for these pro-
 Two other proteins that are important in 
cesses and give skeletal muscle cells their 
muscle contraction and are associated with 
characteristic appearance (Squire  
1981 
). 
the thin fi lament are tropomyosin and tropo-
Within the myofi bril, the less dense I - band is 
nin. Tropomyosin is the second - most abun-
made up primarily of thin fi laments,  while 
dant protein in the thin fi lament and makes 
the A - band is made up of thick fi laments and 
up about 7% of the total myofi brillar protein. 
some overlapping thin fi laments (Goll et al. 
Tropomyosin is made up of two polypeptide 
 1984 ). The backbone of the thin fi laments is 
chains ( alpha and beta ) The alpha chain has 
made up primarily of the protein actin, while 
an approximate molecular weight of 34,000, 
the largest component of the thick fi lament is 
and the beta chain has a molecular weight of 
the protein myosin. Together, these two pro-
approximately 36,000. These two chains 
teins make up nearly 70% of the proteins in 
interact with each other to form a helix. The 
the myofi bril of the skeletal muscle cell. 
native tropomyosin molecule interacts with 
 Myosin is the most abundant myofi brillar 
the troponin molecule to regulate contrac-
protein in skeletal muscle, making up approx-
tion. Native troponin is a complex that con-
imately 50% of the total protein in this organ-
sists of three subunits. These are termed 
elle. Myosin is a negatively charged protein 
troponin I (MW 23,000), troponin C (MW 
with an isoelectric point of 5.3. Myosin is 
18,000), and troponin T (MW 37,000). 
a large protein (approximately 500,000 
Troponin C has the ability to bind calcium  
daltons) that contains six polypeptides. 
released from the sarcoplasmic reticulum, 
Myosin consists of an alpha helical tail (or 
troponin I can inhibit the interaction between 
rod) region that forms the backbone of the 
actin and myosin, and troponin T binds very 
thick fi lament and a globular head region that 
strongly to tropomyosin. The cooperative 
extends from the thick fi lament and interacts 
action of troponin and tropomyosin in 
with actin in the thin fi lament.  The  head 
response to calcium increases in the sarco-
region of myosin also has ATPase activity, 
plasm regulates the interaction between actin 
which is important in the regulation of con-
and myosin and thus is a major regulator of 
traction . Each myosin molecule contains two 
contraction. Calcium that is released from the 
heavy chains (approximately 220,000 daltons 
sarcoplasmic reticulum is bound to the tropo-
Chemistry and Biochemistry of Meat    9
nin complex and the resulting conformational 
 Central to the existence of the muscle cell 
changes within troponin cause tropomyosin 
is the production of adenosine triphosphate 
to move away from sites on actin to which 
(ATP), the energy currency of the cell. ATP 
myosin binds and allows myosin and actin to 
consists of adenosine (an adenine ring and a 
interact. 
ribose sugar ) and three phosphate groups (tri-
 For contraction to occur, the thick and thin 
phosphate). Cleavage of the bonds between 
fi laments interact via the head region of 
the phosphates (P i ) and the rest of the mole -
myosin. The complex formed by the interac-
cule provides energy for many cellular func -
tion of myosin and actin is often referred 
tions, including muscle contraction and the 
to as actomyosin. In electron micrograph 
control of the concentrations of key ions (like 
images of contracted muscle or of postrigor 
calcium) in the muscle cell. Cleavage of P i 
muscle, the actomyosin looks very much like 
from ATP produces adenosine diphosphate 
cross  - bridges between the thick and thin fi la-
(ADP), and cleavage of pyorphosphate (PP i ) 
ments; indeed, it is often referred to as such. 
from ATP produces adenosine monophos-
In postmortem muscle, these bonds are irre-
phate (AMP). Since the availability of ATP 
versible and are also known as rigor bonds, 
is central to survival of the cell, there is a 
as they are the genesis of the stiffness (rigor) 
highly coordinated effort by the cell to main-
that develops in postmortem muscle. The 
tain its production in both living tissue and 
globular head of myosin also has enzymatic 
in the very early postmortem period. 
activity; it can hydrolyze ATP and liberate 
 Muscular activity is dependent on ample 
energy. In living muscle during contraction, 
supplies of ATP within the muscle. Since it 
the ATPase activity of myosin provides 
is so vital, muscle cells have developed  
energy for myosin bound to actin to swivel 
several ways of producing/regenerating ATP. 
and ultimately pull the thin fi laments  toward  
Muscle can use energy precursors stored in 
the center of the sarcomere. This produces 
the muscle cell, such as glycogen, lipids, and 
contraction by shortening the myofi bril,  the 
phosphagens (phosphocreatine, ATP), and it 
muscle cell, and eventually, the muscle. The 
can use energy sources recruited from the 
myosin and actin can disassociate when a 
blood stream (blood glucose and circulating 
new molecule of ATP is bound to the myosin 
lipids). Which of these reserves (intracellular 
head (Goll et al.  1984 ). In postrigor muscle, 
or circulating) the muscle cell uses depends 
the supply of ATP is depleted, resulting in 
on the activity the muscle is undergoing. 
the actomyosin bonds becoming essentially 
When the activity is of lower intensity, the 
permanent.  
muscle will utilize a higher proportion of 
energy sources from the blood stream and 
lipid stored in the muscle cell. These will be 
 Muscle Metabolism 
metabolized to produce ATP using aerobic 
 From a metabolic point of view, energy use 
pathways. Obviously, ample oxygen is 
and production in skeletal muscle is simply 
required for this process to proceed. During 
nothing short of amazing in its range and 
high intensity activity, during which ATP is 
responsiveness. In an actively exercising 
used very rapidly, the muscle uses intracel-
animal, muscle can account for as much as 
lular stores of phosphagens or glycogen. 
90% of the oxygen consumption in the body. 
These two sources, however, are utilized 
This can represent an increase in the mus-
very quickly and their depletion leads to 
cle ’ s metabolic rate of as much as 200% from 
fatigue. This is not a trivial point. 
the resting state (Hargreaves and  Thompson  
Concentration of ATP in skeletal muscle is 
 1999 ). 
critical; available ATP must remain above 
10    Chapter 1
approximately 30% of the resting stores, or 
with ATP (100  mmol/kg dry muscle weight 
relaxation cannot occur. This is because 
for phosphocreatine compared with 25  mmol/
relaxation of contraction is dependent on 
kg dry muscle weight for ATP) but very low 
ATP, which is especially important because 
abundance compared with glycogen (500 
 
removal of calcium from the sarcoplasm is 
mmol/kg dry muscle weight for glycogen). 
an ATP - dependent process (Hargreaves and 
Phosphocreatine can easily transfer a phos-
Thompson   1999 ). 
phate group to ADP in a reaction catalyzed 
 The primary fuels for muscle cells include 
by creatine kinase. This reaction is easily 
phosphocreatine, glycogen, glucose lactate , 
reversible and phosphocreatine supplies 
free fatty acids, and triglycerides. Glucose 
can be readily restored when ATP  demand  
and glycogen are the preferred substrates for 
is low. In living muscle, when activity is 
muscle metabolism and can be utilized either 
intense , this system can be advantageous, as 
aerobically (oxidative phosphorylation) or 
it consumes H 
+ 
 and thus can reduce the 
anaerobically (anaearobic glycolysis). Lipid 
muscle cell acidosis that is associated with 
and lactate utilization require oxygen. Lipids 
anaerobic glycolysis. Another advantage of 
are a very energy - dense storage system and 
the system is that the catalyzing enzyme is 
are very effi cient with respect to the high 
located very close to the actomyosin ATPase 
amount of ATP that can be generated per unit 
and also at the sarcoplasmic reticulum (where 
of substrate. However, the rate of synthesis 
calcium is actively taken up from the sarco-
of ATP is much slower than when glycogen 
plasm to regulate contraction) and at the sar-
is used (1.5  mmol/kg/sec for free fatty acids 
colemma. However, this system is not a 
compared with 3  mmol/kg/sec for glycogen 
major contributor to postmortem metabo-
utilized aerobically and 5  mmol/kg/sec when 
lism, as the supplies are depleted fairly 
glycogen is used in anaerobic glycolysis) 
rapidly. 
(Joanisse   2004 ). 
 
In general, glycogen is the preferred 
 
Aerobic metabolism, the most effi cient 
substrate for the generation of ATP, either 
energy system, requires oxygen to operate, 
through the oxidative phosphorylation or 
and that oxygen is supplied by the blood 
through anaerobic glycolysis (Fig.  1.1 ). One 
supply to the muscle and by the oxygen trans-
of the key steps in the fate of glycogen is 
porter, myoglobin. It has been estimated that 
whether or not an intermediate to the process, 
in working muscle, the myoglobin is some-
pyruvate, enters the mitochondria to be 
where in the neighborhood of 50% saturated . 
completely broken down to CO 
2 
 and H 
2 O 
Under conditions of extreme hypoxia (as 
(yielding 38  mol of ATP per mole of oxidized 
found in postmortem muscle), oxygen sup-
glucose - 1 - P  produced  from  glycogen  or 
plies are depleted because blood fl ow is not 
36 
 mol if the initial substrate is glucose), 
suffi cient (or does not exist ), and myoglobin 
or if it ends in lactate via the anaerobic gly-
oxygen reserves are depleted if this state con-
colysis pathway. The anaerobic pathway, 
tinues long enough. Prior to exsanguination, 
while comparatively less effi cient  (yielding 
the oxidation of glycogen or other substrates 
3    mol  of  ATP  per  mole  of  glucose - 1 - P  pro-
to form water and carbon dioxide via oxida-
duced from glycogen or 2  mol if the initial 
tive phosphorylation is a very effi cient way 
substrate is glucose), is much better at pro-
for the cell to regenerate ATP. However, 
ducing ATP at a higher rate. Early postmor-
after exsanguination, the muscle cell must 
tem muscle obviously uses the anaerobic 
turn solely to anaerobic pathways for energy 
pathway, as oxygen supplies are rapidly 
production. 
depleted. This results in the buildup of the 
 Phosphocreatine in living, rested muscle 
end product, lactate ( lactic acid), resulting in 
is available in moderate abundance compared 
pH decline.  
Chemistry and Biochemistry of Meat    11
  Figure 1.1.    ATP production in muscle.  
 Major Postmortem Changes 
to be between 2 and 2.5  μ M in length. In stri-
in Muscle 
ated muscle, titin thus spans fully half of a 
sarcomere, with its C - terminal end localizing 
 Tenderization 
in the M - line at the center of the sarcomere 
 During refrigerated storage, it is well known 
and the N - terminal forming an integral part 
that meat becomes more tender . It is com-
of the Z - line. Titin aids in maintaining sarco-
monly accepted that the product becomes 
meric alignment of the myofi bril during con-
more tender because of proteolytic changes 
traction. Titin integrates the Z - line and the 
occurring in the architecture of the myofi bril 
thick fi laments, maintaining the location of 
and its associated proteins. There are several 
the thick fi laments between the Z - lines. Titin 
key proteins that are degraded during post-
is also hypothesized to play a role in generat-
mortem aging. 
ing at least a portion of the passive tension 
that is present in skeletal muscle cells. During 
development of the myofi bril, titin is one of 
 Titin 
the earliest proteins expressed, and it is 
 Titin (aka connectin) is a megaprotein that is 
thought to act as a  “ molecular ruler ”  by pro-
approximately 3 megadaltons in size. In 
viding a scaffolding or template for the 
addition to being the largest protein found in 
developing myofi bril ( Clark et al.  2002 ). 
mammalian tissues, it is also the third - most 
 Due to the aforementioned roles of titin 
abundant. A single titin molecule is estimated 
in living cells, it is quite conceivable that 
12    Chapter 1
its degradation in postmortem muscle would 
extends from the Z - line to the pointed ends 
lead to weakening of the longitudinal struc-
of the thin fi lament. The C - terminal end of 
ture of the myofi brillar sarcomere and integ-
nebulin is embedded into the Z - line. Nebulin 
rity of muscle. This weakening, in conjunction 
is highly nonextensible and has been referred 
with other changes in postmortem muscle, 
to as a molecular ruler that during develop -
could lead to enhanced tenderness. The deg-
ment may serve to defi  ne the length of the 
radation of titin has been observed in several 
thin fi laments (Kruger et al.  1991 ). Nebulin, 
studies (Lusby et al.  1983 ; Zeece et al.  1986 ; 
via its intimate association with the thin fi la-
Astier et al.  1993 ; Huff - Lonergan et al.  1995 ; 
ment (Lukoyanova et al.  
2002 
), has been 
Melody et al.  2004 ; Rowe et al.  2004a, b ). 
hypothesized to constitute part of a compos-
When titin is degraded, a major degradation 
ite nebulin/thin fi lament (Pfuhl et al.  1994 ; 
product, termed T 2,  is observed that migrates 
Robson et al.  1995 ) and may aid in anchoring 
only slightly faster under SDS - PAGE con-
the thin fi lament to the Z 
- 
line (Wang and 
ditions than intact titin. This product migrates 
Wright  
1988 
; Komiyama et al.  
1992 
). 
at approximately 2,400 
 kDa (Kurzban and 
Degradation of nebulin postmortem could 
Wang  
1988, 1987 
; Huff 
- 
Lonergan et al. 
weaken the thin fi lament linkages at the 
 
1995 
). Another titin degradation product 
Z 
- 
line, and/or of the thin fi laments in the 
that has been observed by SDS - PAGE an -
nearby I - band regions (Taylor et al.  1995 ), 
alysis migrates at approximately 1,200  kDa 
and thereby weaken the structure of the 
(Matsuura et al.  1991 ; Huff - Lonergan et al. 
muscle cell. Nebulin has also been shown to 
 
1995 
). This latter polypeptide has been 
be capable of linking actin and myosin (Root 
shown to contain the portion of titin that 
and Wang  1994a, b ). It has been hypothe-
extends from the Z - line to near the N 2   line 
sized that nebulin may also have a regulatory 
in the I - band (Kimura et al.  1992 ), although  
function in skeletal muscle contraction (Root 
the exact position that the 1200  kDa polypep-
and Wang  
1994a, b 
; Bang et al.  
2006 
). 
tide reaches in the sarcomere is still not 
Portions of nebulin that span the A - I junction  
certain. The 1,200 - kDa polypeptide has been 
have the ability to bind to actin, myosin, and 
documented to appear earlier postmortem in 
calmodulin (Root and Wang  
2001 
). More 
myofi brils from aged beef that had lower 
interesting, this portion of nebulin (spanning 
shear force (and more desirable tenderness 
the A - I junction) has been shown to inhibit 
scores) than in samples from product that had 
actomyosin ATPase activity (Root and Wang, 
higher shear force and/or less favorable ten-
 2001 ; Lukoyanova et al.  2002 ). This region 
derness scores (Huff - Lonergan et al.  1995, 
of nebulin also has been suggested to inhibit 
1996a, b ). The T2 polypeptide can also be 
the sliding velocities of actin fi laments over 
subsequently degraded or altered during 
myosin. If the latter role is confi rmed, then it 
normal postmortem aging. Studies that have 
is also possible that nebulin 
’ 
s postmortem 
used antibodies against titin have been shown 
degradation may alter actin - myosin  interac-
to cease to recognize T2 after prolonged 
tions in such a way that the alignment and 
periods of postmortem storage or  μ  - calpain 
interactions of thick and thin fi laments  in 
digestion (Ho et al.  
1994 
; Huff 
- 
Lonergan 
postmortem muscle is disrupted. This, too, 
et  al.   1996a )  
could lead to an increase in postmortem ten-
derization. Nebulin degradation does seem to 
be correlated to postmortem tenderization, 
 Nebulin 
although the exact cause - and - effect  relation-
 Nebulin is another mega - protein (Mr 600 –
ship remains to be substantiated (Huff 
 
900 
 
kDa) in the sarcomere. This protein 
 
Lonergan et al.  
1995 
; Taylor et al.  
1995 
; 
Chemistry and Biochemistry of Meat    13
Huff 
- 
Lonergan et al.  
1996a 
; Melody et al. 
related to the shear force (Penny  1976 ; Huff -
 2004 ).  
 Lonergan  et  al.   1996b ;  Huff - Lonergan  and 
Lonergan,  1999 ; Lonergan et al.  2001 ; Rowe 
et  al.   2003 ;  Rowe  et  al.   2004a ).  Troponin - T 
 Troponin -  T  
is a substrate for  μ - calpain, and it is hypoth-
 For many years it has been recognized that 
esized that  μ - calpain is at least partly respon-
the degradation of troponin - T and the appear-
sible for the postmortem degradation of 
ance of polypeptides migrating at approxi-
troponin - T and the concomitant production 
mately 30 
 kDa are strongly related to, or 
of the 28 
- 
 and 30 
- 
kDa polypeptides. 
correlated with, the tenderness of beef (Penny 
Degradation of troponin - T may simply be an 
et al.  
1974 
; MacBride and Parrish  
1977 
; 
indicator of overall postmortem proteolysis 
Olson and Parrish  1977 ; Olson et al.  1977 ). 
(i.e., it occurs as meat becomes more tender). 
It has been shown that purifi ed bovine tropo-
However, because troponin - T is an integral 
nin - T can be degraded by  μ  - calpain  in   vitro  
part of skeletal muscle thin fi laments (Greaser 
to produce polypeptides in the 30 - kDa region 
and Gergely   1971  ), its role in postmortem 
(Olson et al.  1977 ). In addition, polypeptides 
tenderization may warrant more careful 
in the 30 - kDa region found in aged bovine 
examination as has been suggested (Ho et al. 
muscle specifi cally have been shown to be 
 1994 ; Uytterhaegen et al.  1994 ; Taylor et al. 
products of troponin 
- 
T by using  Western  
 1995 ;  Huff - Lonergan  et  al.   1996b ).  Indeed, 
blotting techniques (Ho et al.  1994 ). Often, 
the troponin - T subunit makes up the elon -
more than one fragment of troponin - T can be 
gated portion of the troponin molecule and 
identifi ed in postmortem muscle. Increasing 
through its interaction with tropomyosin aids 
postmortem time has been shown to be asso -
in regulating the thin fi lament during skeletal 
ciated with the appearance of two major 
muscle contraction (Greaser and Gergely 
bands (each is likely a closely spaced doublet 
 1971 ; Hitchcock  1975 ; McKay et al.  1997 ; 
of polypeptides) of approximately 30 and 
Lehman et al.  2001 ). It is conceivable that 
28  kDa, which label with monoclonal anti-
postmortem degradation of troponin 
- 
T and 
bodies to troponin - T (Huff - Lonergan et al. 
disruption of its interactions with other thin 
 1996a ). In addition, the increasing postmor-
fi lament proteins aids in the disruption of the 
tem aging time was also associated with a 
thin fi laments in the I - band, possibly leading  
loss of troponin - T, as has been reported in 
to fragmentation of the myofi bril and overall 
numerous studies (Olson et al.  
1977 
;  muscle integrity. During postmortem aging, 
Koohmaraie et al.  1984a, b ; Ho et al.  1994 ). 
the myofi brils in postmortem bovine muscle 
It has recently been shown that troponin - T is 
are broken in the I - band region (Taylor et al. 
cleaved in its glutamic acid - rich   amino - ter-
 1995 ). Because troponin - T is part of the reg-
minal region (Muroya et al.  
2007 
). Some 
ulatory complex that mediates actin - myosin 
studies have shown labeling of two very 
interactions (Greaser and Gergely,  
1971 
; 
closely spaced bands corresponding to intact 
Hitchcock,  1975 ; McKay et al.  1997 ; Lehman 
troponin - T. This is likely due to isoforms of 
et al.  
2001 
), it is also conceivable that its 
troponin - T that are known to exist in skeletal 
postmortem degradation may lead to changes 
muscle (Briggs et al.  1990 ; Malhotra  1994 ; 
involving thick and thin fi lament  interac-
Muroya et al.  2007 ), including specifi cally 
tions. Regardless of whether or not troponin-
bovine skeletal muscle (Muroya et al.  2007 ). 
- T aids in disruption of the thin fi lament  in 
Both the appearance of the 30 -  and 28 - kDa 
the I 
- 
band, alters thick and thin fi lament 
bands and the disappearance of the intact 
interactions, or simply refl ects overall protein 
troponin - T in the myofi bril are very strongly 
degradation, its degradation and appearance 
14    Chapter 1
of polypeptides in the 30 - kDa region seem to 
myofi 
brils (Huff 
- 
Lonergan et al.  
1996a 
; 
be a valuable indicator of beef tenderness 
Huff - Lonergan  and  Lonergan,   1999 ;  Carlin 
(Olson et al.  1977 ; Olson and Parrish,  1977 ; 
et al.  
2006 
). Thus, the proteolytic enzyme 
Koohmaraie et al.  
1984a, b 
; Koohmaraie 
 μ - calpain may be, at least in part, responsible 
 1992 ;  Huff - Lonergan  et  al.   1995 ;  Huff -
for desmin degradation under normal post-
 Lonergan  et  al.   1996a ;  Huff - Lonergan  and 
mortem aging conditions. Whether or not this 
Lonergan   1999 ).  
degradation is truly directly linked to tender-
ization or is simply an indicator of overall 
postmortem proteolysis remains to be 
 Desmin 
determined.  
 It has been suggested that desmin, an inter-
mediate fi lament protein (O ’  Shea et al.  1979 ; 
 Filamin 
Robson  1989 ) localized at the periphery of 
the myofi brillar Z 
- 
disk in skeletal muscle 
 Filamin is a large ( M r    =    245,000  in  skeletal 
(Richardson et al.  1981 ), plays a role in the 
and cardiac muscle) actin 
- binding  protein 
development of tenderness (Taylor et al. 
that exists in numerous cell types (Loo et al. 
 1995 ;  Huff - Lonergan  et  al.   1996a ;  Boehm  et 
 1998 ; Thompson et al.  2000 ; van der Flier et 
al.  1998 ; Melody et al.  2004 ). The desmin 
al.  
2002 
). There are several different iso-
intermediate fi laments surround the Z - lines 
forms of fi lamin (Hock et al.  
1990 
). The 
of myofi brils. They connect adjacent myofi -
amount of fi lamin in skeletal and cardiac 
brils at the level of their Z 
- 
lines, and the 
muscle is very low (approximately  ≤ 0.1%  of 
myofi brils to other cellular structures, includ-
the total muscle protein). In skeletal and 
ing the sarcolemma (Robson,  1989 ; Robson 
cardiac muscle, fi lamin is localized at the 
et al.  
1995 
). Desmin may be important in 
periphery of the myofi brillar Z - disk, and it 
maintaining the structural integrity of muscle 
may be associated with intermediate fi la-
cells (Robson et al.  1981, 1991 ). It is possible 
ments in these regions (Loo et al.  
1998 
; 
that degradation of structural elements that 
Thompson et al.  2000 ; van der Flier et al. 
connect the major components (i.e., the myo-
 
2002 
). Thus, postmortem degradation of 
fi brils) of a muscle cell together, as well as 
fi lamin conceivably could disrupt key link-
the peripheral layer of myofi brils to the cell 
ages that serve to help hold myofi brils  in 
membrane, could affect the development of 
lateral register. Degradation of fi lamin  may 
tenderness. Desmin is degraded during post-
also alter linkages connecting the peripheral 
mortem storage (Hwan and Bandman  1989 ; 
layer of myofi brils in muscle cells to the sar-
Huff - Lonergan  et  al.   1996a ;  Huff - Lonergan 
colemma by weakening interactions between 
and Lonergan,  
1999 
; Melody et al.  
2004 
; 
peripheral myofi brillar Z - disks and the sarco-
Rowe et al.  
2004b 
; Zhang et al.  
2006 
). 
lemma via intermediate fi lament associations 
Furthermore , it has been documented that 
or costameres (Robson et al.  1995 ). A  study  
desmin is degraded more rapidly in myofi -
using myofi brils from beef showed that some 
brils from samples with low shear force 
fi lamin was degraded to form an approxi-
and higher water 
- 
holding capacity (Huff 
mately 240 
- 
kDa degradation product that 
 Lonergan  et  al.   1996a ;  Huff - Lonergan  and 
migrated as a doublet in both myofi brils from 
Lonergan,  1999 ; Melody et al.  2004 ; Rowe 
naturally aged muscle and in  
μ  - calpain -
et al.  
2004b 
; Zhang et al.  
2006 
). A major 
 digested  myofi brils (Huff 
- 
Lonergan et al. 
degradation product that is often seen in beef 
 1996a ). This same doublet formation (com-
is a polypeptide of approximately 38 
 kDa. 
posed of intact and degraded fi lamin)  has 
This degradation product also has been 
been seen in cultured embryonic skeletal 
shown to be present in  
μ  - calpain - digested 
muscle cells and was attributed to calpain 
Chemistry and Biochemistry of Meat    15
activity (Robson et al.  1995 ). Uytterhaegen 
the total water in muscle cells; depending on 
et al.  (1994)  have shown increased degrada-
the measurement system used, approximately 
tion of fi lamin in muscle samples injected  
0.5 
 g of water per gram of protein is esti -
with CaCl 2 , a process that has been shown to 
mated to be tightly bound to proteins. Since 
stimulate proteolysis and postmortem tender-
the total concentration of protein in muscle 
ization (Wheeler et al.  
1992 
; Harris et al. 
is approximately 200  mg/g, this bound water 
 2001 ). Compared with other skeletal muscle 
only makes up less than a tenth of the total 
proteins, relatively little has been done to 
water in muscle. The amount of bound water 
fully characterize the role of this protein in 
changes very little if at all in postrigor muscle 
postmortem tenderization of beef. Further 
( Offer and Knight  1988b ). 
studies that employ a combination of sen-
 
Another fraction of water that can be 
sitive detection methods (e.g., one 
- 
 and 
found in muscles and in meat is termed 
two - dimensional 
gels, 
Western 
blotting, 
entrapped (also referred to as immobilized) 
immunomicroscopy) are needed to determine 
water (Fennema  1985 ). The water molecules 
the role of fi lamin in skeletal muscle systems 
in this fraction may be held either by steric 
and  postmortem  tenderization.   
( space ) effects and/or by attraction to the 
bound water. This water is held within the 
structure of the muscle but is not bound per 
se to protein. In early postmortem tissue, this 
 Water - Holding Capacity/ Drip  
water does not fl ow freely from the tissue, yet 
Loss Evolution  
it can be removed by drying and can be easily 
 
Lean muscle contains approximately 75% 
converted to ice during freezing. Entrapped 
water. The other main components include 
or immobilized water is most affected by the 
protein (approximately 18.5%), lipids or fat 
rigor process and the conversion of muscle 
(approximately 3%), carbohydrates (approxi-
to meat. Upon alteration of muscle cell struc-
mately 1%), and vitamins and minerals (often 
ture and lowering of the pH, this water can 
analyzed as ash, approximately 1%). The 
also eventually escape as purge (Offer and 
majority of water in muscle is held within the 
Knight   1988b ). 
structure of the muscle and muscle cells. 
 Free water is water whose fl ow from the 
Specifi cally, within the muscle cell, water is 
tissue is unimpeded.  Weak surface forces 
found within the myofi brils, between the 
mainly hold this fraction of water in meat. 
myofi brils themselves and between the myo-
Free water is not readily seen in pre - rigor 
fi brils and the cell membrane (sarcolemma), 
meat, but can develop as conditions change  
between muscle cells, and between muscle 
that allow the entrapped water to move from 
bundles (groups of muscle cells) (Offer and 
the structures where it is found (Fennema 
Cousins   1992 ). 
 1985 ). 
 Water is a dipolar molecule and as such is 
 The majority of the water that is affected 
attracted to charged species like proteins. In 
by the process of converting muscle to meat 
fact, some of the water in muscle cells is very 
is the entrapped (immobilized) water. 
closely bound to protein. By defi nition, 
Maintaining as much of this water as possible 
bound water is water that exists in the vicin-
in meat is the goal of many processors. Some 
ity of nonaqueous constituents (like proteins) 
of the factors that can infl uence the retention  
and has reduced mobility (i.e., does not easily 
of entrapped water include manipulation of 
move to other compartments). This water is 
the net charge of myofi brillar proteins and 
very resistant to freezing and to being driven 
the structure of the muscle cell and its com-
off by conventional heating (Fennema  1985 ). 
ponents (myofi brils, cytoskeletal linkages, 
True bound water is a very small fraction of 
and membrane permeability), as well as the 
16    Chapter 1
amount of extracellular space within the 
relaxation (Millman et al.  
1981 
; Millman 
muscle itself.  
et al.  1983 ). This would indicate that in living 
muscle the amount of water within the fi la-
mentous structure of the cell would not nec-
 Physical/Biochemical Factors 
essarily change. However, the location of this 
in Muscles That Affect 
water can be affected by changes in volume 
Water - Holding Capacity 
as muscle undergoes rigor. As muscle goes 
 
During the conversion of muscle to meat, 
into rigor, cross 
- 
bridges form between the 
anaerobic glycolysis is the primary source of 
thick and thin fi laments, thus reducing avail-
ATP production. As a result , lactic acid 
able space for water to reside (Offer and 
builds up in the tissue, leading to a reduction  
Trinick  1983 ). It has been shown that as the 
in pH of the meat. Once the pH has reached 
pH of porcine muscle is reduced from physi-
the isoelectric point (pI) of the major pro-
ological values to 5.2 – 5.6 (near the isoelec-
teins, especially myosin (pI   =   5.3), the net 
tric point of myosin), the distance between 
charge of the protein is zero , meaning the 
the thick fi laments declines an average of 
numbers of positive and negative charges 
2.5  nm (Diesbourg et al.  1988 ). This decline 
on the proteins are essentially equal. These 
in fi lament spacing may force sarcoplasmic 
positive and negative groups within the 
fl uid from between the myofi laments to the 
protein are attracted to each other and result 
extramyofi brillar space. Indeed, it has been 
in a reduction in the amount of water that can 
hypothesized that enough fl uid may be lost  
be attracted and held by that protein. 
from the intramyofi brillar space to increase 
Additionally, since like charges repel, as the 
the extramyofi brillar volume by as much as 
net charge of the proteins that make up the 
1.6 times more than its pre 
- 
rigor volume 
myofi bril approaches zero (diminished net 
(Bendall and Swatland  1988 ). 
negative or positive charge), repulsion of 
 
During the development of rigor, the 
structures within the myofi bril is reduced, 
diameter of muscle cells decreases (Hegarty 
allowing those structures to pack more 
 
1970 
; Swatland and Belfry  
1985 
) and is 
closely together. The end result of this is a 
likely the result of transmittal of the lateral 
reduction of space within the myofi bril. 
shrinkage of the myofi brils to the entire cell 
Partial denaturation of the myosin head at 
(Diesbourg et al.  1988 ). Additionally, during 
low pH (especially if the temperature is still 
rigor development, sarcomeres can shorten; 
high) is also thought to be responsible for a 
this also reduces the space available for water 
large part of the shrinkage in myofi brillar 
within the myofi bril. In fact, it has been 
lattice spacing (Offer  1991 ). 
shown that drip loss can increase linearly 
 Myofi brils make up a large proportion of 
with a decrease in the length of the sarco-
the muscle cell. These organelles constitute 
meres in muscle cells (Honikel et al.  1986 ). 
as much as 80 
– 
90% of the volume of the 
More recently, highly sensitive low 
- 
fi eld 
muscle cell. As mentioned previously, much 
nuclear magnetic resonance (NMR) studies 
of the water inside living muscle cells is 
have been used to gain a more complete  
located within the myofi bril. In fact, it is esti-
understanding of the relationship between 
mated that as much as 85% of the water in a 
muscle cell structure and water distribution 
muscle cell is held in the myofi brils.  Much 
(Bertram et al.  
2002 
). These studies have 
of that water is held by capillary forces 
suggested that within the myofi bril, a higher 
arising from the arrangement of the thick and 
proportion of water is held in the I - band than 
thin fi laments within the myofi bril. In living 
in  the  more  protein - dense  A - band.  This 
muscle, it has been shown that sarcomeres 
observation may help explain why shorter 
remain isovolumetric during contraction and 
sarcomeres (especially in cold  
- 
shortened 
Chemistry and Biochemistry of Meat    17
muscle) are often associated with increased 
associated with intermediate fi lament  struc-
drip losses . As the myofi bril shortens and 
tures and structures known as costameres. 
rigor sets in, the shortening of the sarcomere 
Costameres provide the structural framework 
would lead to shortening and subsequent 
responsible for attaching the myofi brils to the 
lowering of the volume of the I - band region 
sarcolemma. Proteins that make up or are 
in myofi bril. Loss of volume in this myofi -
associated with the intermediate fi laments 
brillar region (where much water may reside), 
and costameres include (among others ) 
combined with the pH - induced lateral shrink-
desmin, fi lamin, synemin, dystrophin, talin, 
age of the myofi bril, could lead to expulsion 
and vinculin (Greaser  1991 ). If costameric 
of water from the myofi brillar  structure 
linkages remain intact during the conversion 
into the extramyofi brillar spaces within the 
of muscle to meat, shrinkage of the myofi -
muscle cell (Bendall and Swatland  1988 ). In 
brils as the muscle goes into rigor would be 
fact, recent NMR studies support this hypoth-
transmitted to the entire cell via these pro-
esis (Bertram et al.  2002 ). It is thus likely that 
teinacious linkages and would ultimately 
the gradual mobilization of water from the 
reduce volume of the muscle cell itself (Offer 
intramyofi brillar spaces to the extramyofi -
and Knight  1988b ; Kristensen and Purslow 
brillar spaces may be key in providing a 
 2001 ; Melody et al.  2004 ). Thus, the rigor 
source of drip. 
process could result in mobilization of water 
 
All the previously mentioned processes 
not only out of the myofi bril, but also out of 
infl uence the amount of water in the myofi -
the extramyofi bril spaces as the overall 
bril. It is important to note that shrinkage of 
volume of the cell is constricted. In fact, 
the myofi brillar lattice alone could not be 
reduction in the diameter of muscle cells has 
responsible for the movement of fl uid to the 
been observed in postmortem muscle (Offer 
extracellular space and ultimately out of the 
and Cousins  1992 ). This water that is expelled 
muscle. The myofi brils are linked to each 
from the myofi bril and ultimately the muscle 
other and to the cell membrane via proteina-
cell eventually collects in the extracellular 
cious connections (Wang and Ramirez 
space. Several studies have shown that gaps 
 
Mitchell  
1983 
). These connections, if they 
develop between muscle cells and between 
are maintained intact in postmortem muscle, 
muscle bundles during the postrigor period 
would transfer the reduction in diameter of 
(Offer et al.  1989 ; Offer and Cousins  1992 ). 
the myofi brils to the muscle cell (Diesbourg 
These gaps between muscle bundles are 
et al.  1988 ; Morrison et al.  1998 ; Kristensen 
the primary channels by which purge is 
and Purslow  
2001 
; Melody et al.  
2004 
). 
allowed to fl ow from the meat; some inves -
Myofi bril shrinkage can be translated into 
tigators have actually termed them  
“ 
drip 
constriction of the entire muscle cell, thus 
channels. ”    
creating channels between cells and between 
bundles of cells that can funnel drip out 
 Postmortem Changes in Muscle 
of the product (Offer and Knight  
1988 
). 
That Infl uence Quality 
Extracellular space around muscle fi  bers  con-
tinually increases up to 24 hours postmortem, 
 
As muscle is converted to meat, many 
but gaps between muscle fi ber  bundles 
changes occur, including: (1) a gradual deple-
decrease slightly between nine and 24 hours 
tion of available energy; (2) a shift from 
postmortem, perhaps due to fl uid  outfl ow 
aerobic to anaerobic metabolism favoring the 
from these major channels (Schafer et al. 
production of lactic acid, resulting in the pH 
 2002 ).  These  linkages  between  adjacent 
of the tissue declining from near neutrality to 
myofi brils and myofi brils and the cell mem-
5.4 – 5.8; (3) a rise in ionic strength, in part, 
brane are made up of several proteins that are 
because of the inability of ATP 
- 
dependent 
18    Chapter 1
calcium, sodium , and potassium pumps to 
that is involved in increasing the tenderness 
function; and (4) an increasing inability of 
of fresh meat and in infl uencing fresh meat 
the cell to maintain reducing conditions. All 
water - holding  capacity  (Huff - Lonergan  and 
these changes can have a profound effect on 
Lonergan  
2005 
). Because  
μ  - calpain  and 
numerous proteins in the muscle cell. The 
m 
- 
calpain enzymes contain both histidine 
role of energy depletion and pH change have 
and SH - containing cysteine residues at their 
been covered in this chapter and in other 
active sites, they are particularly susceptible 
reviews (Offer and Trinick  1983 ; Offer and 
to inactivation by oxidation (Lametsch et al. 
Knight  1988a ). What has not been as thor-
 
2008 
). Therefore, oxidizing conditions in 
oughly considered is the impact of other 
postmortem muscle lead to inactivation or 
changes on muscle proteins, such as oxida-
modifi cation of calpain activity (Harris et al. 
tion and nitration. 
 2001 ; Rowe et al.  2004a, b ; Maddock et al. 
 2006 ). In fact, evidence suggests oxidizing 
conditions inhibit proteolysis by  μ  - calpain, 
 Protein Oxidation 
but might not completely inhibit autolysis 
 Another change that occurs in postmortem 
(Guttmann et al.  1997 ; Guttmann and Johnson  
muscle during aging of whole muscle prod-
 1998 ;  Maddock  et  al.   2006 ).  In  postmortem 
ucts is increased oxidation of myofi brillar 
muscle, there are differences between 
and sarcoplasmic proteins (Martinaud et al. 
muscles in the rate that postmortem oxidation 
 1997 ; Rowe et al.  2004a, b ). This results in 
processes occur (Martinaud et al.  1997 ). It 
the conversion of some amino acid residues, 
has been noted that differences in the rate of 
including histidine, to carbonyl derivatives 
oxidation in muscle tissue are seen when 
(Levine et al.  1994 ; Martinaud et al.  1997 ) 
comparing the same muscles between animals  
and can cause the formation of intra  -  and/or 
and/or carcasses that have been handled dif-
inter - protein  disulfi de  cross - links  (Stadtman 
ferently (Juncher et al.  2001 ). These differ -
 1990 ; Martinaud et al.  1997 ). In general, both 
ences may arise because of differences in 
these changes reduce the functionality of pro-
diet , breed, antemortem stress , postmortem 
teins in postmortem muscle (Xiong and 
handling of carcasses, etc. In fact, there have 
Decker  
1995 
). In living muscle, the redox 
been reports of differences between animals 
state of muscle can infl uence  carbohydrate 
and between muscles in the activity of some 
metabolism by directly affecting enzymes in 
enzymes involved in the oxidative defense 
the glycolytic pathway. Oxidizing agents can 
system of muscle (Daun et al.  
2001 
). 
also infl uence glucose transport. Hydrogen  
Therefore, there may be genetic differences 
peroxide (H 2 O 2 ) can mimic insulin and stim -
in susceptibility to oxidation that could be 
ulate glucose transport in exercising muscle. 
capitalized on to improve meat quality. It is 
H 2 O 2  is increased after exercise, and thus oxi-
reasonable to hypothesize that differences in 
dation systems may play a role in signaling 
the antioxidant defense system between 
in skeletal muscle (Balon and Yerneni  2001 ). 
animals and/or muscles would infl uence 
Alterations in glucose metabolism in the 
calpain activity, proteolysis, and thus 
ante  -  and perimortem time period do have the 
tenderization. 
potential to cause changes in postmortem 
  Exposure to oxidizing conditions (H 2 O 2 ) 
muscle metabolism and thus represent an 
under postmortem 
- 
like conditions inhibits 
important avenue of future research. 
calpain activity (Carlin et al.  
2006 
). In a 
 
In postmortem muscle, these redox  series of in vitro assays using either a fl uo-
systems may also play a role in infl uencing 
rescent peptide or purifi ed myofi brils as the 
meat quality. The proteolytic enzymes, the 
substrate it was shown that the presence of 
calpains, are implicated in the proteolysis 
oxidizing species does signifi cantly  impede 
Chemistry and Biochemistry of Meat    19
the ability of calpains to degrade their sub-
(NOS). There are three major isoforms of 
strates. Oxidation with H 
2 O 2  
signifi cantly 
NOS: neural, inducible, and endothelial. 
limits proteolytic activity of  μ  -   and  m - calpain 
Skeletal muscle expresses all three isoforms; 
against the fl uorescent  peptide  Suc - Leu - 
however, the neural form, nNOS, is thought 
Leu - Val - Tyr - AMC,  regardless  of  the  pH  or 
to be the predominant isoform (Kaminski and 
ionic strength. Similar results were seen 
Andrade  2001 ). These enzymes utilize argi-
when using purifi ed  myofi brils as the sub-
nine as a substrate and catalyze the following 
strate. This inhibition was reversible, as 
reaction:  L - arginine+NADPH+O 2   forming 
addition of reducing agent (DTT) to the oxi-
L - citrulline+  •  NO+NADPH + . NO is important 
dized samples restored activity. Oxidation 
in biological systems, particularly because of 
also has been shown to slow the rate of  μ -
its role as a second messenger. However, 
 
calpain autolysis and could be part of the 
while NO rapidly diffuses through tissues, 
mechanism underlying some of the retarda-
NO itself is a relatively short - lived species. 
tion of activity (Guttmann et al.  1997 ; Carlin 
It does have the ability to combine with other 
et al.  2006 ). 
biomolecules that also have physiological 
 Oxidation does occur early in postmortem 
importance . 
meat, and it does infl uence proteolysis (Harris 
 
One example of this is its ability to 
et al.  2001 ; Rowe et al.  2004b ). Rowe et al. 
combine with superoxide to form the highly 
 (2004)  showed that there was a signifi  cant  
oxidizing molecule peroxynitrite. Proteins 
increase in proteolysis of troponin - T in steaks 
are important biological targets of peroxyni-
from  alpha - tocopherol - fed  steers  after  2   days  
trite, particularly proteins containing cyste-
of postmortem aging compared with steers 
ine, motioning, and/or tryptophan (Radi et al. 
fed a conventional feedlot diet. This indicates 
 
2000 
). Several enzymes are known to be 
that very low levels of oxidation can infl u-
inactivated by peroxynitrite. Among these is 
ence proteolysis and that increasing the level 
the sarcoplasmic reticulum Ca 
2+  - ATPase 
of antioxidants in meat may have merit in 
(Klebl et al.  
1998 
). One indirect effect of 
improving tenderness in future studies. In 
NO is S 
- 
nitrosylation. In most cases , S 
- 
fact, low levels of oxidation may be the cause 
nitrosylation events involve amines and 
of some heretofore - unexplained variations in 
thiols. Nitric oxide can interact with cyste-
proteolysis and tenderness that have been 
ines to form nitrosothiols that can alter the 
observed in meat.  
activity of the protein. Because of this, it 
has been suggested that S - nitrosylation may 
function as a post - translational modifi cation 
 Nitric Oxide and  S  - Nitrosylation 
much like phosphorylation (Jaffrey et al. 
 Nitric oxide (NO) is often used as a general 
 2001 ). Some proteins, such as the ryanodine 
term that includes NO and reactive nitrogen 
receptor and the cysteine protease caspase - 
species (RNS), like S 
- 
nitrosothyols, per-
3, have been shown to be endogenously 
oxynitrate, and metal NO complexes. In 
nitrosylated, further supporting the sugges-
living tissue, NO is involved in arteriole dila-
tion that formation of nitrosothiols may be 
tion that increases blood fl ow to muscles, 
an important regulatory step (Hess et al. 
resulting in increased delivery of nutrients 
 2001 ; Hess et al.  2005 
).  μ  - Calpain  is  also 
and oxygen to the muscle (Kobzik et al. 
a cysteine protease that could be infl uenced 
 1994 ; Stamler et al.  2001 ). NO species are 
by S 
- 
nitrosylation. Small thiol peptides 
also implicated in glucose homeostasis and 
like glutathione can be impacted by nitro -
excitation - contraction coupling. The gas NO 
sative stress to form compounds like 
is produced in biological systems by a family 
S - nitrosoglutathione  (GSNO).  These  com-
of enzymes known as nitric oxide synthases 
pounds can, in turn, infl uence other proteins 
20    Chapter 1
    Bang ,   M. - L.  ,    X.    Li  ,    R.    Littlefi eld  ,    S.    Bremner  ,    A.    Thor  , 
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 Aspects of skeletal muscle function that 
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- 
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nance study 
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Chapter 2
 Technological Quality of Meat for Processing  
 Susan   Brewer  
 
 Introduction 
 Breed Effects on Quality of Meat 
 For the purposes of this discussion, techno -
 Livestock breed can affect the quality char -
logical quality of meat for processing includes 
acteristics of the meat produced, either 
the factors that affect meat quality in general, 
because the breed has naturally adapted to 
whether endogenous or exogenous. Factors 
stressful environmental conditions or because 
that contribute to the quality of the meat for 
two or more breeds have been purposefully 
processing include the breed of the animal 
crossbred to increase prevalence of desirable 
and its associated characteristics, gene status 
qualities. Often these modifi cations improve 
within breed, diet and plane of nutrition, 
one set of attributes at the expense of another. 
fatness/leanness, rate of postmortem pH and 
 
For example, Brahman cattle are used 
temperature decline, and postmortem han-
extensively in the southwestern United States 
dling such as aging. Ultimately, meat quality 
because of their tolerance to adverse environ-
is defi ned in terms of consumer acceptability, 
mental conditions; however, Brahman car-
which include tenderness, juiciness and 
casses have tenderness issues . Toughness of 
fl avor, and appearance characteristics such as 
meat from Brahman cattle has been associ-
color, amount of fat, amount of visible water, 
ated with high levels of calpastatin in the 
and textural appearance, which have a sig-
muscle (Ibrahim et al.  2008 ). The Japanese 
nifi cant impact on consumer expected satis-
Wagyu breed produces highly marbled, 
faction (Brewer et al.  1998, 2001 ). Because 
tender meat. Cross breeding Brahman with 
they are the most important traits defi ning 
Wagyu cattle to produce Waguli cattle, which 
consumer acceptance, tenderness and fl avor 
have a high degree of marbling and low cal-
consistency are important (Robbins et al. 
pastatin activity in the tissue, results in more 
 
2003 
). Factors contributing to the sensory 
tender meat immediately after slaughter. 
quality characteristics of meat include breed 
Tenderness of meat from Brahman cattle 
(Cameron et al.  1990 ; Lan et al.  1993 ), intra-
does catch up with suffi cient aging (14 
 d). 
muscular fat content (Brewer et al.  
2001 
; 
Schone et al.  (2006)  reported initial tender-
Rincker et al.  2008 ), calpastatin and  μ  - calpain 
ness differences in beef from Holstein and 
gene status (Casas et al.  
2006 
), Halothane 
Simmental cattle, in addition to different 
gene status (Sather et al.  1990 ; Leach et al. 
responses to aging. Some breed differences 
 1998 ), ryanodine receptor gene status (Fujii 
(Nelore, Simmental, Simbrasil) in initial 
et al.  
1991 
), diet, antemortem handling 
postmortem beef tenderness are lost after 7 
(Ohene - Adjai et al.  2003 ), and ultimate pH 
days of aging (Bianchini et al.  
2007 
). 
(Zhu  and  Brewer   1998 ).  
According to Hocquette et al.  (2006) , cattle 
25
26    Chapter 2
of different breeds or different genotypes 
polymorphisms within the gene for bovine 
of the same breed differ primarily in their 
leptin, a chemical messenger that affects feed  
connective tissue characteristics (collagen 
intake, fatness (fat yield and subcutaneous 
cross 
- 
linking and solubility), content, and 
fat), and tenderness. 
composition of intramuscular fat and/or the 
 Thomas et al.  (2008)  reported that beef 
characteristics of their muscle fi bers  (slow -
from medium - framed, early maturing animals 
 oxidative,  fast - oxidoglycolytic,  fast  glyco-
had the highest marbling scores, and had the 
lytic). Mutations in the myostatin gene result 
highest concentration of total n - 3 fatty acids, 
in muscle hypertrophy, producing cattle with 
and the lowest n 
- 
6/n 
- 
3 ratio . Lynch et al. 
enlarged muscles. However, this mutation 
 
(2002) 
 reported that meat from Hereford 
favors glycolytic muscle fi ber  metabolism 
cattle had higher levels of C14:0, C16:1, and 
and decreases collagen and intramuscular fat 
C18:0 in the phospholipid fraction than that 
contents, favoring tenderness. 
from Friesian and Charolais cattle. 
 
Collagen constitutes 20 
– 
25% of the 
 Breed can also have signifi cant effects on 
protein in mammals, and connective tissues 
beef fl avor.  Nitrogen -   and  sulfur - compounds, 
are composed mainly of collagen. It occurs 
free amino acids, alcohols, aldehydes, and 
in muscle tissue, binding the fi bers together 
ketones in the fl avor volatiles differ in the 
in bundles. However, collagen is not distrib-
meat from different breeds of cattle (Sato et 
uted uniformly among muscle groups.  al.  
1995 
; Insausti et al.  
2005 
). Beef from 
Generally, the collagen content parallels the 
Friesian cattle has a stronger fatty fl avor 
level of physical activity of the particular 
and aftertaste, and a different volatile profi le 
muscle. Increasing intermolecular cross - link-
than that from Pirenaica cattle (Gorraiz et al. 
ing among collagen molecules decreases 
 2002 ). Enzymes, such as  μ  -   and  m - calpain, 
their extensibility and their solubility (Forrest 
known primarily for textural changes, can 
et al.  
1975 
). Those muscles that are used 
infl uence  fl avor by producing peptides that 
extensively have higher amounts of collagen 
make signifi cant  fl avor contributions. Meat 
and are generally tougher. 
from  Bos taurus  and  Bos indicus  cattle inher-
 Smith et al.  (2007a)  reported that weight 
iting the CC genotype at the calpastatin 
at slaughter, hot carcass weight, loin muscle 
gene and the TT genotype at the  μ  - calpain 
area, yield grade , calpastatin enzyme activ-
gene produce steaks with more intense fl avor 
ity, and carcass quality grade were relatively 
(Casas et al.  
2006 
). These genes correlate 
highly heritable. They found moderate heri-
with increased rancid , sour , and salty fl avors, 
tability estimates for marbling score , back  
and decreased umami fl avor 
(Toldr á  
fat thickness, and feedlot average daily gain. 
and Flores  
2000 
). In addition, content of 
MacNeil et al.  (2001)  reported that Limousin -
several volatile compounds, such as hexane 
 sired calves grew more rapidly than Hereford -
and 2,2,4,6,6 
- 
pentamethylheptane, differs 
 
sired calves. By the fi nishing  phase, 
be  tween Friesian and Pirenaica cattle (Gorraiz 
Limousin 
- 
 and Hereford 
- 
sired calves had 
et al.  2002 ). Breed also affects beef color. 
greater average daily gains than Piedmontese -
Frickh and Solkner  (1997)  reported that beef 
 sired calves. A clear stratifi cation of USDA 
from Holstein cattle had higher a 
* 
 values 
yield grade, based on differences in carcass 
(redness) than did Simmental and Simmental 
weight, longissimus muscle area, fat depth, 
x Limousin cattle. 
and percentage kidney, pelvic, and heart fat, 
 
Genetic differences in swine have also 
existed, depending on sire breed. Hereford -
resulted in pork with different quality char-
 sired calves had more marbling than progeny 
acteristics. Since 1990, producers have dra-
of Limousin or Piedmontese sires. Schenkel 
matically improved the nutritional profi le of 
et al.  (2005)  reported associations between 
pork, producing a product that is 31% lower 
Technological Quality of Meat for Processing    27
in fat, 10% lower in cholesterol and 17% 
while that from Duroc and Duroc/Hampshire 
lower in calories (USDA  
2007 
). However, 
was lower in fat. Pork from Danish Landrace 
genetic selection for leanness has not been 
Duroc pigs was more tender than that from 
without unintended consequences. Pigs  Landrace, Duroc, and various crosses with 
homozygous for the Halothane gene (nn) 
Yorkshire pigs. Blanchard et al.  
(1999) 
 
have higher gain: feed ratios, and their car-
reported that meat from crossbred pigs that 
casses are leaner than those from Halothane 
were at least half Duroc were more tender 
negative (NN) and heterozygotic (Nn) pigs 
than that from Large White and British  
(Leach et al.  1996 ). While pigs carrying one 
Landrace crosses. Brewer et al.  (2002)  also 
or two copies of the Halothane gene have 
reported that pork from Duroc - sired pigs is 
higher lean content, they are likely to produce 
more tender than that from Duroc/Landrace -  
pale, soft, and exudative (PSE) meat that has 
and  Pietrain - sired  pigs. 
excessive drip loss because of rapid pH 
 
Wood et al.  
(2004) 
 reported that breed 
decline while the carcass is still hot (Sather 
affected the fatty acid composition of intra-
et al.  1990 ). Fernandez et al.  (2004)  reported 
muscular neutral lipid. Pork from Berkshire 
that NN and Nn pigs exhibited postmortem 
and Tamworth pigs (fatter carcasses) had 
changes at the same rate, as evidenced by 
more 14:0 and 16:0, while that from Duroc 
similar glycogen, lactate, creatine phosphate 
and Large White (leaner) contained more 
and ATP levels, and pH values at 40 minutes 
polyunsaturated fatty acids. Meat from Duroc 
postmortem. Raw meat (longissimus lumbo-
pigs had high concentrations of 20:5n - 3 and 
rum) from nn pigs had lower visual color 
22:6n - 3. 
intensity and homogeneity scores than meat 
 Genetic markers for tenderness have been 
from NN and Nn pigs. Meat from nn pigs was 
identifi ed for Duroc - Landrace pigs (Rohrer et 
less tender than that from NN pigs; the Nn 
al.   2006 ).  Chromosome  2  region  60 – 66    cM 
pigs were intermediate. 
appears to be associated with all measures of 
 
Meat from pigs (Swedish Hampshire x 
pork tenderness and the region on chromo-
Finnish Landrace) that are homozygous 
some 17 (32 
– 39    cM)  was  associated  with 
and heterozygous for the rendement napole 
measures of intramuscular fat and loineye 
(RN - ; acid meat) allele has been shown to be 
area.  
juicier than that from noncarriers. The RN -  
allele also contributes to tenderness (Josell et 
 Diet Effects on Meat Quality 
al.  
2003 
). Emnett  
(1999) 
 reported that 
Berkshire and Chester White pigs had lower 
 Diet can contribute to meat quality directly 
glycolytic potential (thought to be an indica -
(compounds from the feed source deposit in 
tor of the RN 
- 
 allele) than Hampshire or 
the meat) or indirectly (primarily by increas-
Hampshire crossbred pigs. High glycolytic 
ing fatness). Feeding fi sh byproducts, raw 
potential values were associated with lower 
soybeans, canola oil, and meal can result in 
pH, poorer WHC, higher cooking loss, and 
undesirable fl avors in meat (Melton  1990 ). 
paler color. 
Pork fat is more likely to be affected by alter-
 Meat derived from pigs of these very dif-
ation of dietary fat source than is beef fat 
ferent genetic backgrounds does differ in 
because pigs have little capacity to biohydro-
quality characteristics (Brewer et al.  2002 ). 
genate unsaturated fats , depositing them in 
Ellis et al.  (1996)  reported that Duroc pigs 
tissues in much the same form as they were 
produce meat that is highly marbled and has 
consumed. Feeding pigs high levels of PUFA 
good eating quality. Brewer et al.  
(2004) 
 
decreases saturation of carcass fat and has 
reported that meat from Duroc/Landrace -  and 
detrimental effects on pork quality (Whitney 
Large White 
- 
sired pigs was higher in fat, 
et al.  2006 ). Unsaturated fatty acids result in 
28    Chapter 2
carcass fat that is soft and oily. In addition, 
higher the phospholipid concentration (Larick 
carcass fat that is higher in PUFA content is 
et  al.   1989 ).  Feedlot - fi nished cattle have a 
more susceptible to oxidation during storage 
different fatty acid profi le from forage 
- 
fed 
than fat that contains more saturated fat. 
cattle. Meat from forage 
- 
fed beef contains 
Palm oil and whole linseed supplements 
more linolenic acid, and less oleic and lin-
increase muscle levels of alpha 
- linolenic 
oleic acids than that from concentrate 
- 
fed 
(C18:3) and EPA (eicosapentaenoic acid 
beef (Elmore et al.  
2004 
). Intense pasture 
[C20:5]); fi sh oil increases EPA and DHA 
rotation systems of millet and grain have 
(docosahexaenoic acid [C22:6]; Elmore et al. 
been shown to alter concentrations of diter-
 2004 ). The effects of changes in dietary fat 
penoids and lactones (Maruri and Larick 
source on pork fat are more apparent if they 
 
1992 
). Lactones correlate positively with 
occur during the last few weeks before  
roasted beef fl avor and negatively with 
slaughter than if they occur 1 to 2 months 
gamey/stale  off - fl avor; diterpenoids posi -
before slaughter. 
tively correlate with gamey/stale off - fl avor. 
 Lampe et al.  (2006)  reported that while 
Differences in oleic, linoleic and linolenic 
fi nishing diet (yellow corn , white corn, 1/3 
acids, diterpenoids, and lactones may be 
yellow corn and 2/3 white corn, 2/3 yellow 
responsible for fl avor differences. Nelson et 
corn and 1/3 white corn, or barley) altered 
al.  (2004)  found that adding restaurant grease 
saturated,  mono -   and  poly - unsaturated  fatty 
to cattle diets to increase energy intake 
acid content in the subcutaneous fat of pigs, 
increased initial tenderness and had no effect 
energy source had little effect on the eating 
on drip or cook loss, sustained tenderness, 
quality of pork. However Wood et al.  (2004)  
juiciness, and beef fl avor. 
reported that a low 
- 
protein fi nishing  diet 
 Feeding antioxidants has been of signifi -
increased tenderness and juiciness but  cant interest with respect to maintaining post -
decreased fl avor quality of pork. 
 
harvest meat quality (Guo et al.  
2006 
). 
 
Rosenvold et al.  
(2001) 
 reported that 
Vitamin E locates in the cell membrane in 
feeding fi nishing diets low in digestible car-
proximity to phospholipids. It can prevent  
bohydrate can reduce muscle glycogen stores 
development of free radicals in membranes 
in slaughter pigs without compromising 
ante 
- 
 and postmortem (Onibi et al.  
2000 
). 
growth rate. This diet reduced  
μ  - calpain 
Garber et al.  (1996)  reported that vitamin E 
activity and increased calpastatin activity, 
supplementation increased muscle alpha 
indicating less muscle protein degradation in 
 
tocopherol levels, delaying metmyoglobin 
the muscles compared to muscles of control 
formation (beef) and lipid oxidation in a 
animals. In an effort to improve the nutri-
dose - dependent manner. Boler et al.  (2009)  
tional profi le of pork, Janz et al.  (2008)  fed 
found that feeding natural sources of vitamin 
pigs a plant - based diet containing conjugated 
E to fi nishing pigs was more effective in 
linoleic acid, selenium, and vitamin E. The 
reducing lipid oxidation of pork during sub-
dietary treatments had some effects on meat 
sequent storage and display than were artifi -
quality, but the overall effects on appearance 
cial sources. Yang et al.  (2002)  found that 
and palatability were small. 
meat from pasture 
- 
fed cattle contained as 
 Diet can shift the bone/muscle/fat ratio of 
much  alpha - tocopherol  as  grain - fed  cattle 
beef carcasses. Grain feeding (high 
- 
energy 
supplemented with 2500 
 
IU vitamin E. It 
diet) usually increases carcass weight and 
contained a higher percentage of linolenic 
intramuscular fat content, and produces more 
acid, a lower percentage of linoleic acid, and 
intense fl avor in red meats than do low 
was less prone to lipid oxidation and devel -
 energy forage and grass diets (Melton  1990 ). 
opment  of  warmed - over  fl avor. Diet can also 
The longer the animal is in the feedlot, the 
affect color of the resultant meat. Vitamin E 
Technological Quality of Meat for Processing    29
supplemented into swine diets has been 
been used as indicators of meat quality. 
shown to stabilize meat color and decrease 
Highly marbled meat has traditionally been 
fl uid loss when fed at  
> 200   mg/kd  of  diet 
thought to be the ideal because of the effects 
during fi nishing (Asghar et al.  1980 ). 
of fat on fl avor and tenderness. However, 
 Shifting carcass bone/muscle/fat ratio can 
Rincker et al.  (2008)  reported that intramus-
also be accomplished with steroid - like drugs. 
cular fat (0.8 
– 
8.0%) explained less than 
Feeding beta 
- 
agonists can have signifi cant 
15% of the variance in pork fl avor  scores. 
effects on feedlot performance and/or carcass 
Consumers could tell no difference in pork 
characteristics. Quinn et al.  (2008)  reported 
fl avor scores until the fat content reached 
that feeding ractopamine 
- 
hydrochloride to 
4.5%. In addition, visible fat content in pork 
fi 
nishing heifers generally improved the 
is a major determinant of purchase intent 
effi ciency of carcass gain with minimal effect 
with consumers preferring leaner products 
on marbling score, yield grade, loin muscle 
(Brewer et al.  
2001 
; Rincker et al.  
2008 
). 
area, or percentages of carcasses grading 
Fernandez et al.  
(1999) 
 reported that pork 
USDA  Choice . Avendano 
- 
Reyes et al.  texture and taste are enhanced at intramuscu-
 (2006)  reported that feeding either zilpaterol -  
lar fat levels up to 3.25%, but inconsistent 
or  ractopamine - hydrochloride  considerably 
effects occurred with respect to tenderness/
improved  gain - to - feed  ratio,  hot  carcass 
toughness. 
weight, and carcass yield. Zilpaterol increased 
 Ellis et al.  (1996)  reported that longissi-
loin muscle area. Both beta 
- agonists 
mus muscle from pig genotypes selected for 
decreased meat tenderness compared with 
the propensity to increase marbling are more 
controls. Smith et al.  (2007b)  reported that 
tender and juicy, and have lower shear values. 
implanting anabolic steroids increased hot 
The Duroc breed produces pork that is highly 
carcass weight and loin muscle area for both 
marbled with good eating quality (Ellis et al. 
heifers and steers. However, implants had no 
 
1996 
). Brewer et al.  
(2002) 
 reported that 
effect on dressing percent , fat thickness, 
chops from Duroc and Pietrain pigs had the 
yield grade, marbling score, intramuscular 
most visible marbling, while those from 
lipid content, or concentrations of major fatty 
Duroc/Landrace and Large White had the 
acids. 
least. Chops from Duroc, Duroc/Hampshire, 
 
Montgomery et al.  
(2004) 
 reported that 
and Pietrain pigs had the highest fat content. 
supplementation of three biological types of 
Meat from these breeds, however, differs 
cattle (Bos indicus, Bos Taurus - Continental, 
from other breeds with regard to muscle fi ber 
Bos Taurus 
- 
English ) with vitamin D3 (0.5 
type and the incidence of PSE ( Chang et al. 
million IU/d) for 8 days prior to slaughter 
 2003 ). 
improved tenderness by affecting muscle 
 
Cattle breeds with different growth 
Ca ++ 
 concentrations, calpain activities , and 
rates but the same degree of marbling differ 
muscle proteolysis.  
substantially in tenderness and Warner 
Bratzler shear value (Chambaz et al.  2003 ). 
Historically, selection of beef breeds has 
 Marbling Effects on 
been based on marbling, irrespective of 
Meat Quality 
growth rate and simultaneous selection pres-
 A high plane of nutrition, especially during 
sure for reduced overall fat deposition.  
the fi nishing phase, can increase intramuscu-
lar fat to a greater or lesser degree depending 
 Postmortem  p  H  Decline 
on species, breed, animal age, and a variety 
of other factors. The fatness and marbling 
 
Postmortem biochemical changes dramati-
associated with a high plane of nutrition have 
cally affect tenderness and fl avor. The loss of 
30    Chapter 2
circulatory competency after harvest requires 
 
1979 
). During the immediate postmortem 
that the tissues shift to anaerobic metabolism, 
period, tissues metabolize glycogen via 
resulting in the accumulation of metabolic 
anaerobic pathways, lowering pH. ATP is 
byproducts, including lactic acid, in the 
rapidly consumed, but as reducing equiva-
muscle. The pH declines from about 6.8 to 
lents are consumed, it is not regenerated. 
5.7. Endogenous thiol proteinases (cathep-
Without the plasticizing effect of ATP, actin 
sins B and L) become activated near pH 5.4. 
and myosin cross - link, the sarcomere short-
They are redistributed (intracellularly) during 
ens, fi bers contract, and rigor results. During 
aging (Spanier et al.  1990 ; Spanier and Miller  
the rigor process, muscle cells undergo both 
 1993 ). Proteolytic enzyme activity is temper -
longitudinal and lateral contraction, usually 
ature - dependent; some (cathepsins B and L) 
within 24 hours. WHC decreases during the 
retain high activity levels even at cooking 
postmortem period. Rigor mortis occurs in 
temperatures (70 ° C). Pigs with defects in the 
beef when the pH drops to 5.9 (Honikel et al. 
ryanodine receptor gene (rn+) undergo exces-
 
1981 
). Factors that affect the rate of pH 
sive (not necessarily rapid) pH decline, 
decline, such as Halothane gene status of pigs 
resulting in abnormally acidic conditions in 
and residual glycogen in the tissues, affect 
the meat, which affects water - holding capac-
tenderness, WHC, and color. Factors that 
ity, tenderness, and color (Leach et al.  1996 ; 
affect the ultimate pH (ryanodine gene status, 
Bidner et al.  2004 ). 
stress that alters muscle glycogen content) 
 
Water 
- 
holding capacity (WHC) is the 
also affect these characteristics.  
ability of meat to hold onto its own or added 
 The peak solubility of actin and myosin 
water when force ( heat , pressure ) is applied. 
occurs between pH 5.7 and 6.0 (Scopes 
Water is the major component (about 75%) 
 1964 ). It decreases dramatically as pH drops 
of muscle tissue. Most exists in layers around 
from 6.0 to 5.6. These proteins are almost  
polar molecules and between layers of cel-
completely insoluble below pH 4.9. 
lular materials. The majority is located in the 
Sarcoplasmic proteins are soluble between 
intermolecular spaces between the salt - solu-
4.8 and 5.2, regardless of temperature; 
ble proteins (actin, myosin) of muscle tissue, 
however, at or above 37  ° C, even high pH 
which varies depending on various intrinsic 
will not prevent them from precipitating onto 
and extrinsic factors (Offer and Knight  1988 ). 
myofi brillar proteins. This decreases WHC 
Its movement is restricted in a number of 
as well as other quality characteristics of 
ways that are dependent primarily on the 
meat.  The  minimum  water - holding  capacity 
myofi laments. Some of the factors that alter 
of meat occurs around pH 5.0, which corre-
the spatial arrangement of the myofi laments 
sponds to the isoelectric point of actomyosin. 
include alterations in net charge induced by 
In addition, toughness is negatively corre-
pH changes, screening of charges by anions/
lated with initial pH and rate of pH decline 
cations, presence of divalent cations (Mg ++ , 
(Zamora  et  al.   1996 ).  Two - thirds  of  the  WHC 
Ca ++ ), denaturing conditions that alter protein 
losses occurring during rigor are due to loss 
conformation (rapid pH decline while the 
of ATP, with the remainder due to pH decline. 
carcass temperature is still high), and pres-
The rate of pH decline is partially genetic, in 
ence of plasticizing agents such as ATP and 
that pH decreases more rapidly in meat from 
enzymes (ATPase). 
some breeds, because of the fi ber - type  distri-
 In  pre - rigor  meat,  Mg - ATP = 
 serves to 
bution in the muscle tissue, than it does in 
prevent cross - linking between the contractile 
meat from other breeds. Brewer et al.  (2002)  
proteins, actin and myosin (Fig.  2.1 ). This 
reported that carcasses from Duroc and Large 
maintains the interfi lamental space such that 
White pigs experienced postmortem purge 
water can move in (Siegel and Schmidt  
losses of 5 – 6%, while those from Pietrain, 
Technological Quality of Meat for Processing    31
 Figure 2.1.    Effect of excess hydrogen ion (pH decrease) on water located in muscle tissue.  
Duroc/Landrace, and Duroc/Hampshire  drip loss, poor  WHC, and pale color of pale, 
experienced purge losses of 12 
– 
13%.  soft exudative (PSE) pork (Bendall and 
Genetics appears to play a signifi cant role in 
Wismer - Pedersen   1962 ).  Development  of  the 
WHC. 
PSE condition may also be due to denatur-
 In addition to pH decline, alterations in 
ation and precipitation of sarcoplasmic pro-
carcass temperature can have signifi cant 
teins onto myofi brillar proteins (Joo et al. 
effects on meat quality (tenderness and 
 1999 ).  The  genetic  profi le of pigs that produce 
WHC). Loss of circulatory and respiratory 
PSE pork is advantageous for production 
competencies at slaughter allows accumula-
reasons . Brewer et al.  (2002)  reported that 
tion of metabolic heat. Carcass temperatures 
chops from Duroc 
- 
sired pigs were more 
can increase to over 42  ° C during the fi rst 
tender than those from Duroc/Landrace 
- 
 
45 – 60 minutes postmortem. At this tempera-
and Pietrain - sired pigs. Brewer et al.  (2002)  
ture, a rapid pH decline can result in denatur-
reported  similar  effects  on   “ texture ”   of 
ation of myofi brillar proteins such that WHC 
chops from Halothane positive (nn) and neg-
is ultimately quite low, even if ultimate pH 
ative (NN) Pietrain, RN 
- 
 Hampshire, rn+ 
(24  h) is within normal ranges . Rapid post-
Hampshire, Berkshire, and Duroc lines of 
mortem glycolysis is associated with the high 
pigs. 
32    Chapter 2
 Hambrecht et al.  (2005)  reported that high 
of biohydrogenation of dietary lipids, or via 
stress conditions (long transport, short  endogenous synthesis. Increased marbling, 
lairage) decreased muscle glycolytic poten -
because of the increased amount of fat avail-
tial and increased plasma lactate, cortisol, 
able for formation of fl avor compounds, has 
muscle temperature, rate of pH decline, ulti-
traditionally been considered to have a rela-
mate pH, and b 
* 
 values (yellowness) of 
tively large impact on the ultimate fl avor of 
pork. Other color measures were unaffected 
the meat product.  
by high stress but water - holding properties 
  “ Meaty  fl avor, ”   the  generic  background 
were impaired. Because supplemental dietary 
fl avor of all types of red meat, is associated 
magnesium is related to postmortem glyco-
with the lean portions of meat. Phospholipids 
gen breakdown of lactic acid and concomi-
(0.5 – 1% of the lean tissue) contain a high 
tant muscle pH decline, it has been shown 
proportion of fatty acids with four or more 
to help offset damage to color and water 
double bonds (C18:4, C20:4, C20:5, C22:5, 
 holding capacity that result from the stress 
C22:6; Table  
2.2 
) that are susceptible to 
involved in transport and handling (Frandson 
oxidation and likely to make specifi c fl avor 
and Spurgeon  1992 ). Feeding swine magne-
contributions to the meat (Elmore et al. 
sium during the fi nishing phase results in 
 
1999 
). Endogenous antioxidant enzymes, 
higher initial and/or ultimate muscle pH 
especially catalase and GSH - Px, can poten-
values and a decrease in the incidence of 
tially delay the onset of oxidative rancidity 
PSE (D 
’ 
Souza et al.  
1998 
; Swigert et al. 
(Pradhan et al.  2000 ). Some meat processing 
 2004 ).  
operations reduce the activity of these 
systems (Decker and Mei  1996 ). Of the 60 -
  plus compounds that contribute specifi cally 
  Flavor  
to  “ meaty ”  aromas, most are sulfur -  or car-
bonyl - containing  compounds  (Shahidi   1994 ). 
 Meaty Flavor 
Phospholipids are also the source of several 
 “ Flavor ”  results from the combination of the 
sulfi des that are generated when they react  
basic tastes ( sweet , sour, bitter, salt, umami) 
with cysteine and/or ribose to produce mild , 
derived from water - soluble compounds and 
slightly meaty - fl avor/odor compounds, such 
odors derived from a variety of substances 
as  2 - methyl - 3 - [methylthio]thiophene  (Rowe 
present in the raw meat. Flavor -  and odor -
 2002 ).    
 active volatiles include alcohols, aldehydes, 
aromatic compounds, esters, ethers, furans, 
 Species - Specifi c Flavor 
hydrocarbons, ketones, lactones, pyrazines, 
pyridines, pyrroles, and sulfi des  (Shahidi 
 Species - specifi c  fl 
avor has traditionally 
 1994 ). The relationship between some of the 
been associated with the lipid portion 
more common volatiles and their respective 
of meat. It may result from quantitative dif-
fl avors is shown in Table  2.1 .  
ferences  of  several  compounds  (3,5 - dimethyl -
 The lipids present in muscle tissue (sub-
 1,2,4,trithiolane, 
2,4,6 - trimethylperhydro - 
cutaneous fat, intramuscular fat, intermuscu-
1,3,5 - dithiazine, 
mercaptothiophenes, 
lar fat, intramyocellular lipid, and structural 
mercaptofurans; Shahidi et al.  1994 ). A beef -
phospholipids) at slaughter serve as a source 
 like aroma compound, 12 - methyltridecanal, 
of many of these fl avor  constituents.  These 
is an important contributor to species fl avor 
lipids are composed of fatty acids that may 
(Mottram et al.  
1982 
). It occurs in much 
be saturated, unsaturated and/or methyl 
smaller amounts in species other than beef. 
 
branched (Fig.  
2.2 
). They may be derived 
Other species 
- specifi c  fl avor  compounds 
directly from the diet, produced as the result 
include 
2 - methyl - 3 - [methyl] - furan 
and 
 Table 2.1.    Flavors and aromas associated with volatile compounds in meat 
   Compound  
   Flavors  and  Aromas  
  Pentanal  
  Pungent  
  Hexanal  
  Green ,  grassy,  fatty  
  Heptanal  
  Green,  fatty,  oily  
  Nonanal  
  Soapy  
  Methional  
  Cooked   potato  
  12 - methyltridecanal  
  Beefy  
  Nona - 2(E) - enal  
  Tallowy,  fatty  
  Deca - 2(E),  4(E) - dienal  
  Fatty,  fried  potato  
  Butanoic  Acid  
  Rancid  
  Hexanoic  Acid  
  Sweaty  
  3 - Hydroxy - 2 - butanone  
  Buttery  
  2 - propanone  
  Livery  
  2,3 - Octanedione  
  Warmed  over  fl avor, lipid oxidation  
  1 - Octen - 3 - ol  
  Mushroom  
  2 - Pentyl  furan  
  Metallic,  green,  earthy,  beany  
  2 - methyl - 3 - [methylthio]furan  
  Meaty,  sweet,  sulfurous  
  4 - hydroxy - 5 - methyl - 3(2H) - furanone  (HMF)  
  Meaty  
  Pyrazines  
  Nutty,  cracker - like,  roasted  
 Amino acids: glycine, alanine, lysine, cysteine, methionine, 
  Sweet  
glutamine, succinic  
  Organic acids: lactic, inosinic, ortho - phosphoric, and pyrrolidone 
  Sweet  
carboxylic  
  Amino  acids:  aspartic  acid,  histidine,  asparagines  
  Sour  
 Organic acids: succinic, lactic, inosinic, ortho - phosphoric, 
  Sour  
pyrrolidone carboxylic  
  Hypoxanthine,  anserine,  carnosine  
  Bitter  
  Amino  acids:  arginine,  leucine,  tryptophan  
  Bitter  
 Monosodium glutamate (MSG), inosine and guanosine 
  Savory,  brothy,  beefy.  
monophosphate (IMP,GMP)  
  Bis(2 - methyl - 3 - furyl)  disulfi de  
  Roasted  meat  
  2 - methyl - 3 - furanthiol  
  Roasted  meat  
  4 - hydroxy - 5 - methyl - 3(2H) - furanone  (HMF)  
  Meaty  
  4 - hydroxy - 2,5 - dimethyl - 3(2H) - furanone  
  Meaty  
  3 - hydroxy - 4,5 - dimethyl - 2(5H) - furanone  
  Meaty  
 MacLeod and Ames,  1986 ; Ha and Lindsay,  1991 ; Spanier et al.,  1992 ; Spanier and Miller,  1993 ; MacLeod,  1994 ; 
Imafi don and Spanier,  1994 ; Maga,  1998 ; Mottram,  1998 ; Shahidi,  1998 ; Rowe,  2002 ; Gorraiz et al.,  2002 . 
 Figure 2.2.    Triglyceride with saturated, mono - unsaturated, and poly - unsaturated fatty acid.  
33
34
 Table 2.2.    Fatty acid composition of selected types of meat  1    
   Total  lipid 
   Total  sat. 
   12:0  
   14:0  
   16:0  
   18:0  
   16.1  
   18.1  
   20:1  
   22:1  
   18:2  
   18:3  
   18:4  
   20:4  
   20:5 
   22:5 
   22:6 
g/100    g  
fatty acids  
 n     −  3 
 n     −  3 
 n     −  3 
   
Chicken  2    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
 Breast  3.57  
  1.01  
  0  
  0.3  
  0.69  
  0.25  
     
0.15   
   
1.03     
  0.03  
  0  
     
0.59     
  0.03  
  0  
  0.06  
  0.01  
  0.01  
  0.02  
    
 Dark  9.73  
  2.66  
  0.03  
  0.07  
  1.84  
  0.63  
     
0.49   
   
2.97     
  0.05  
  0  
     
1.87     
  0.09  
  0  
  0.14  
  0.01  
  0.03  
  0.05  
   
Turkey    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
 Breast  3.46  
  2.10  
  0  
  0.01  
  0.05  
  1.28  
     
0.40   
   
1.98     
  0.01  
  0.01  
     
1.45     
  0.08  
  0  
  0.16  
  0  
  0  
  0  
    
 Dark  7.22  
  2.45  
  0.02  
  0.05  
  1.28  
  0.72  
     
0.24   
   
1.35     
  0.03  
  0.02  
     
1.75     
  0.07  
  0  
  0.26  
  0  
  0.04  
  0.06  
   
Beef 3    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
 3.54  
  1.31  
  0  
  0.09  
  0.78  
  0.43  
     
0.11   
   
1.31     
  0  
  0  
     
0.12     
  0.01  
  0  
  0.02  
  0  
  0  
  0  
   
Pork 3    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
 3.53  
  1.21  
  0.01  
  0.45  
  0.76  
  0.38  
     
0.10   
   
1.42     
  0.02  
  0.30  
     
0.30     
  0  
  0  
  0  
  0  
  0  
  0  
   
Lamb 4    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
 9.23  
  3.30  
  0.02  
  0.24  
  1.79  
  1.10  
   —     
   —     
   —     
   —     
     
0.63   
   
0.12     
  0.09  
   —     
   —     
   —     
   —     
   
Ocean Perch   
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
 2.09  
  0.31  
  0  
  0.08  
  0.18  
  0.04  
     
0.10   
   
0.27     
  0.13  
  0.29  
     
0.04     
  0.0  
  0.03  
  0.01  
  0.10  
  0.03  
  0.30  
   
Atlantic Salmon    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
 12.35  
  2.50  
   —     
  0.57  
  1.90  
  0.32  
     
0.77   
   
2.05     
  1.37  
   —     
     
0.67     
   —     
   —     
  1.27  
  0.69  
   —     
  1.46  
   
Tuna   
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
 5.97  
  0.95  
  0.009  
  0.011  
  0.152  
  0.051  
     
0.025       
0.018     
  0.007  
  0.014  
     
0.008       
0.012     
  0.005  
  0.028  
  0.037  
  0.013  
  0.18  
    
1 Source:    USDA National Nutrient Database for Standard Reference, Release 20 (2007) 
  http://www.nal.usda.gov/fnic/foodcomp/cg i - bin/    
   
2 Chicken, broilers or fryers, separable fat, raw; contains less than 0.5  g 4:0, 6:0, 8:0, and 10:0  
   
3 Beef, top sirloin, separable lean only, trimmed to 1/8 ″  fat, select , raw; contains less than 0.5  g 4:0, 6:0, 8:0, and 10:0  
   
4 Lamb, domestic, rib, separable lean only, trimmed to 1/4 ″  fat, choice, raw  
Technological Quality of Meat for Processing    35
3 - methylcyclopentanone 
(Imafi don 
and 
 Sex and carcass maturity also affect off -
Spanier   1994 ).  Methyl - branched  compounds 
 fl avors. Beef from bulls has a more livery, 
appear to arise from phosphoglycerides 
bloody fl avor than that from heifers, which 
(Werkoff et al.  1993 ; Mottram  1998 ). These 
appears to be related to higher 2 - propanone 
compounds are affected by diet, breed, and 
and ethanol contents (Gorraiz et al.  2002 ). 
muscle. 
To the extent that carcass maturity affects 
 
Muscles vary in their concentrations of 
iron content, it can increase metallic, rancid, 
compounds important to meat fl avor/odor. 
bloody, salty, and bitter fl avor notes (Calkins 
Stetzer et al.  
(2008) 
 reported that beef 
 
2006 
). Volatile compounds impact these 
 Complexus  contained twice the concentration 
fl avor notes as well. Higher concentrations of 
of 2,3 
- 
octanedione, nonanal, and butanoic 
phospholipids, phosphatidylcholine, and 
acid, and 30% more hexanoic acid than the 
phosphatidylethanolamine increase livery 
 Gludeus medius ,   Rectus femoris ,   Vastus lat-
and ammonia fl avors in beef (Larick et al. 
eralic ,   Vastus medialis ,   Psoas major ,  and 
 
1989 
). Several muscles ( 
Triceps brachii , 
 Longissimus dorsi .  
 Vastus lateralis 
, and  
Vastus intermedius ) 
with livery off 
- 
fl avor have more heptanol, 
hexanal,  hexanol,  B - pinene,  1 - octene - 3 - ol, 
 Off - Flavors 
and nonanal. 
 Muscle tissue also contains compounds that 
 Because of their effects on desirable and 
contribute  to  off - fl 
avors in the fi nished 
undesirable fl avor components, diet, animal 
product as a result of genetics, sex of the 
sex, age at slaughter, genetics, and muscle 
animal, heme content of the muscle tissue, 
must be considered when meat tissues are to 
and diet. Livery fl avor is an objectionable, 
be used for specifi c products (fresh, whole 
off - fl avor in beef that increases as iron 
cuts vs. cured, smoked products).  
content increases (Campo et al.  1999 ; Calkins 
and Cuppett  
2006 
; Yancey et al.  
2006 
). 
 Factors Affecting 
Sulfur 
- 
containing compounds (thiols, sul-
Tenderness/Texture 
fi des, thiazoles, sulfur - substituted furans) can 
interact with carbonyl compounds to produce 
 In general, consumers rate tenderness as the 
a livery fl 
avor (Werkhoff et al.  
1993 
). 
major factor that determines the eating 
Muscles often exhibiting liver  
- 
like fl avor, 
quality of meat (Brewer and Novakofski 
such as the  Psoas major  (loin) and  Gluteus 
 
2008 
). Tenderness embodies all the mouth 
medius  ( round ), have higher levels of heme 
feel characteristics perceived kinesthetically: 
iron and/or myoglobin (Yancey et al.  2006 ). 
those perceived prior to mastication ( particle  
Compared with beef  
Infraspinatus ,   Psoas 
size, oiliness), during mastication (tender-
major 
, and  
Rectus femoris 
, the  
Gluteus 
ness, juiciness), and after mastication (fi brous 
medius  had the highest liver off - fl avor score 
residue, mouth coating ; Bourne  
1992 
). 
(Stetzer et al.  
2007 
). Of the  
Complexus , 
Tenderness is composed of mechanical 
 Serratus ventralis ,   Vastus lateralis ,   Vastus 
(hardness, cohesiveness, elasticity), particu-
medialis , and  Longissimus dorsi , the  Vastus 
late (grittiness and fi brousness), and chemi -
lateralis  had the highest liver off - fl avor score 
cal components (juiciness and oiliness; 
and the  
Longissimus dorsi 
 had the lowest 
Bourne  1992 ). Minimally, meat tenderness is 
(Stetzer et al.  
2006 
). Stetzer et al.  
(2008) 
 
affected by myofi brillar, connective tissue, 
reported that livery off - fl avor was positively 
and compositional components. The myofi -
correlated with pentanal, hexanal, 3 - hydroxy -
brillar component can be affected by cold 
 2 - butanone,  and  hexanoic  acid. 
shortening and proteolytic degradation; the 
36    Chapter 2
connective tissue component can be affected 
animals and among muscles within an animal; 
by animal age, degree of activity, mechanical 
this may relate to initial tenderness 
tenderization, and composition ( Pearson and 
(Novakofski and Brewer  2006 ; Stolowski et 
Young  1989 ). Muscle foods have an inherent 
al.  2006 ). A major factor in this variation is 
set of textural characteristics associated with 
high growth rate that requires a high plane of 
them by the nature of the raw material. These 
nutrition. During growth, rapid protein turn-
include fi bers,  fl uid/fat exudation, and con-
over increases proteolytic activity, which 
nective tissue. Textural parameters of interest 
contributes to the aging process (Zgur et al. 
are those that are affected by these raw mate-
 
2003 
). This increased proteolytic activity 
rials characteristics as well as those that are 
enhances aging because proteolytic cathep-
affected by exogenously induced alterations 
sins degrade some structural proteins, allow-
(formulation, aging). 
ing the sarcomere to relax (Kristensen and 
 Tenderness of the fi nal product depends 
Purslow  
2001 
). This allows the infl ow  of 
on the muscle(s) from which the meat was 
water previously expelled during rigor. This 
derived. Beef  Psoas major  was more tender 
infl ow may be driven by the difference in 
than the  Gluteus medius ,   Infraspinatus ,  and 
protein concentration existing between intra -  
 Rectus femoris  (Stetzer et al.  2007 ). Of the 
and extracellular compartments of the muscle 
 Complexus ,   Serratus ventralis ,   Vastus later -
cell. 
alis ,   Vastus medialis , and  Longissimus dorsi , 
 
Tenderness improvement with aging 
the  Longissimus dorsi  was the most tender 
varies between animals within a breed, and 
and the  Vastus lateralis  was the least (Stetzer 
between muscles within an animal. It depends 
et al.  2006 ). In general, meat that is the most 
on several factors that may also be related to 
tender is derived from muscles that were 
initial tenderness (Wicklund et al.  
2005 
; 
least used when the animal was alive , while 
Novakofski and Brewer  2006 ). Wicklund et 
meat that is the most tough is derived from 
al.  (2005)  reported that changes in tenderness 
muscles that are used the most (locomotor, 
of strip steaks required 14 days of aging. 
postural). However, both genetics and age 
Novakofski and Brewer  (2006)  reported that 
affect tenderness. Meat from two 
- 
year  
- 
old 
the mean improvement in shear with aging 
Angus/Wagyu heifers was as tender and 
over the fi rst week differed depending on the 
juicy as that from yearlings. However, meat 
shear value starting point ( original shear 
from two - year - old pure Angus lines was less 
value); however, no differences occurred 
tender and juicy than that from yearlings or 
between 7 and 14 days. Rentfrow et al.  (2004)  
that from Angus/Wagyu animals (Rentfrow 
reported that Warner Bratzler shear values 
et  al.   2004 ).  
decreased and tenderness increased in beef 
from  one -   and  two - year - old  heifers  during 
aging; however, maximum improvement 
 Aging 
occurred after only 7 days of aging. Bruce et 
al.  (2005)  indicated that aging for up to 14 
 Aging Effects on Tenderness 
days increased tenderness.  
 Sarcomere length, muscle, connective tissue 
proteins, and proteolytic degradation account 
 Aging Effects on Flavor 
for most of the variation in tenderness 
(Koohmaraie et al.  
2002 
). Tenderness   
The effects of aging on fl avor are unclear 
depends, in part, on proteolytic degradation 
(Mottram  1998 ). It can alter the makeup of 
of structural and myofi brillar  proteins 
the aroma and fl avor precursors, which ulti-
(Koohmaraie et al.  2002 ). Large variation in 
mately affects the characteristics of the 
aging - induced  improvement  occurs  among 
cooked product. Aging can increase carbon-
Technological Quality of Meat for Processing    37
yls derived from lipid oxidation, which may 
(Fe 3+ , Table  2.3 ). Oxygen can bind to heme 
contribute  to  off - fl avors, decrease fl avor 
iron only if it is in the ferrous state (Fe 2+ ). 
identity, and increase metallic fl avor (Yancey 
However, many other ligands (CN, NO, CO, 
et al.  2005 ). It can also increase fatty fl avor 
N 3 ) can bind to either the ferrous (Fe 2+ )  or 
and negative attributes such as painty, 
ferric (Fe 3+ ) form. Water (H 2 O) can bind to 
cardboard, bitter, and sour (Spanier et al. 
myoglobin (Mb) only if the iron is in the 
 
1992 
; Gorraiz et al.  
2002 
; Bruce et al. 
ferrous form. Under low oxygen tension con-
 2005 ).  Positive  fl 
avor compounds, such 
ditions, Mb exists in the purple 
- colored, 
as  3 - hydroxy - 2 - butanone,  2 - pentyl  furan, 
reduced form (Fe 2+ ). Exposed to oxygen for 
2,3 - octanedione,  and  1 - octene3 - ol,  decrease 
a short period of time, the central iron (Fe 2+ ) 
with aging; and negative compounds, such as 
reversibly binds oxygen, producing oxymyo-
pentanal, nonanal, and butanoic acid, increase 
globin (MbO 2 ), which is bright pink or red. 
with aging (Stetzer et al.  2008 ). Aging beef 
However, when exposed to O 2  for an extended 
can result in changes in umami taste. 
period, the central iron atom can lose an elec-
Glutamic acid content more than doubles 
tron (oxidized to Fe 3+ ), producing metmyo-
during the fi rst 7 days of aging (Bauer  1983 ). 
globin (MetMb), which is grey 
- brown . 
 The potential benefi ts of aging for selected 
Immediately post slaughter, the oxidized 
muscles for fl avor development and tender-
form can be reduced by endogenous reducing 
ization must be weighed against the potential 
systems in the meat, as long as reducing 
development  of  off - fl avors.   
equivalents (NADH) are available and the 
globin fraction is in its native state (undena-
tured). Over time, these reducing equivalents 
 Color 
are depleted and the pigment is irreversibly 
 Color and appearance of fresh meat are major 
oxidized. Oxidation also occurs rapidly if the 
factors in consumer purchase decisions 
globin moiety is denatured by rapidly declin-
because they are presumed to be indicators 
ing pH while the carcass is  “ hot ”  or by exces-
of meat freshness and quality (Brewer et al. 
sively low ultimate pH.  
 2002 ). Meat color is due to the concentration 
 In pigs, color variations may have been 
of heme pigments (myoglobin, hemoglobin), 
inadvertently selected for as pigs were bred 
their chemical states, and the light - scattering 
for high gain/feed ratios and leanness. Brewer 
properties of the meat (Lawrie  2002 ). At high 
et al.  (2002)  reported that genetic line had 
pH, the heme iron is predominantly in the 
signifi cant effects on a 
* 
 value (redness), 
ferrous state (Fe 
2+ 
); low pH accelerates 
which ranged from 9.2 to 11 (on a 15 - point 
ferrous iron conversion to the ferric state 
scale ) among pigs from genetic lines known 
 Table 2.3.    Characteristics of various states of myoglobin 
   Pigment  
   Ligand  
   Conditions  
   Iron  State  
   Color  
  Deoxymyoglobin  
  H 2 O  
  Very  low  oxygen  tension 
  Fe ++   
  Purple - red/purple - pink  
(  24  
    
  IIR   2006   
  Lamb  steaks  
  12  
    
  18  
  24  
    
  IIR   2006   
  Pork  
  2  to  6  
    
  4  to  12  
  8  to  15  
  10  
  ASHRAE   2006   
  Pork  
    
  3  
    
  6  
  12  
  Lawrie  and  Ledward 
 2006   
  Pork  carcasses  
  6  
    
  10  
  15  
    
  IIR   2006   
  Pork  steaks/cuts  
  6  
    
  10  
  15  
    
  IIR   2006   
  Sliced  bacon  (vac.)  
  12  
    
  12  
  12  
    
  IIR   2006   
  Liver  
  4  
    
  12  
  18  
    
  IIR   2006   
Freezing/Thawing    115
1200
1000
800
600
400
Storage life of beef (days)
200
0
–40
–30
–20
–10
0
Temperature (°C)
 Figure 5.2.    Experimental data on the frozen storage life of beef at different temperatures.  
storage, but considerable scatter between 
and have asked whether there is any real eco-
results  at  any  one  temperature.     
nomic advantage in very low temperature 
 
There is some evidence that consumer 
preservation.  
panels are often not very sensitive to quality 
changes. In a study on the quality of lamb 
 Temperature Fluctuation 
stored at  
− 5 ° C  and   − 35 ° C,  a  consumer 
panel could not tell the difference between 
 Generally,  fl uctuating temperatures in storage 
samples, although a trained taste panel could 
are considered to be detrimental to the 
differentiate and scored the samples stored 
product. However, it has been reported that 
at  
− 5 ° C  as  rancid  (Winger   1984 ).  Some 
repeated freeze - thaw cycles do not cause any 
researchers, such as Jul  (1982) , have ques -
essential change in the muscle ultrastructure 
tioned the wisdom of storage below  − 20 ° C 
(Carrol et al.  1981 ) and that several freeze -
1200
1000
800
600
400
Storage life of pork (days)
200
0
–40
–30
–20
–10
0
Temperature (°C)
 Figure 5.3.    Experimental data on the frozen storage life of pork at different temperatures.  
116    Chapter 5
1200
1000
800
600
400
Storage life of lamb (days)
200
0
–40
–30
–20
–10
0
Temperature (°C)
 Figure 5.4.    Experimental data on the frozen storage life of lamb at different temperatures.  
 
thaw cycles during a product 
’ 
s life cause 
 Packaging 
only small quality damage (Wirth  1979 ) or 
possibly no damage at all. In fact, a slight but 
 Packaging has a large direct effect on storage 
signifi cant improvement in samples that had 
life, especially in fatty meats and meat prod-
been frozen and unfrozen several times was 
ucts, and in extreme cases, indirectly due to 
found by one taste panel (Jul  1982 ). 
substantially increasing the freezing time. A 
 Minor temperature fl uctuations in a stored 
number of examples have occurred where 
product are generally considered unimpor-
large pallet loads of warm boxed meat have 
tant, especially if they are below  − 18 ° C  and 
been frozen in storage rooms . In these cases, 
are only of the magnitude of 1 to 2 ° C. Well -
freezing times can be so great that bacterial 
 
packed products and those that are tightly 
and enzymic activity results in a reduction of 
packed in palletized cartons are also less 
storage life. 
likely to show quality loss. However, poorly 
 In most cases, it is the material and type 
packed samples are severely affected by the 
of packaging that infl uence frozen storage 
temperature swings. There is disagreement 
life. Without wrapping, freezer burn may 
on how much effect larger temperature fl uc-
occur, causing extreme toughening and the 
tuations have on a product. Some authors  
development of lipid oxidation as the surface 
consider temperature fl uctuations to have the 
dries, allowing oxygen to reach subcutaneous 
same effect on the quality of the product as 
fat in the affected area. Wrapping in a tightly 
storage at an average constant temperature 
fi tting pack having a low water and oxygen 
(Dawson  1971 ); others consider that fl uctua-
permeability (such as a vacuum pack) can 
tions may have an additive effect (Van Arsdel 
more than double the storage life of a product. 
 1969 ;  Bech - Jacobsen  and  B ø gh - S ø rensen 
Waterproof packing also helps to prevent 
 
1984 
). There is evidence that exposure to 
freezer burn, and tight packing helps to 
temperatures warmer than  − 18 ° C   rather   than 
prevent an ice buildup in the pack. When a 
temperature fl uctuations may be the major 
product is breaded, packaging appears to 
factor infl 
uencing quality deterioration  have little effect, and in a trial where breaded 
(Gortner et al.  1948 ).  
pork chops and breaded ground pork were 
Freezing/Thawing    117
packed in poor and very good packs, an 
of meat. During the freezing operation , 
effect of packing could not be found. 
surface temperatures are reduced rapidly, and 
Lighting, especially ultraviolet, can also 
bacterial multiplication is severely limited, 
increase lipid oxidation (Volz et al.  
1949 
; 
with bacteria becoming completely dormant 
Lentz,  1971 ). Exposure to the levels of light 
below  − 10 ° C. In the thawing operation, these 
found in many retail frozen food display 
same surface areas are the fi rst to rise in tem-
areas can cause appreciable color change 
perature, and bacterial multiplication can 
within 1 to 3 days. Development of off fl avor 
recommence. On large objects subjected to 
can be accelerated and may be noticeable 
long uncontrolled thawing cycles, surface 
within 1 to 2 months on display. Products 
spoilage can occur before the center regions 
kept in dark or opaque packages may there-
have fully thawed . 
fore be expected to retain color longer than 
 Most systems supply heat to the surface 
those exposed to the light.  
and then rely on conduction to transfer that 
heat into the center of the meat. A few use 
electromagnetic radiation to generate heat 
within the meat. In selecting a thawing 
 Thawing and Tempering Systems 
system for industrial use, a balance must be 
for Meat 
struck between thawing time, appearance, 
 
Frozen meat as supplied to the industry 
the bacteriological condition of the product, 
ranges in size and shape, although much of it 
processing problems such as effl uent  dis-
is in blocks packed in boxes. Thawing is 
posal, and the capital and operating costs of 
usually regarded as complete when the center 
the respective systems. Of these factors, 
of the block has reached 0 ° C, the minimum 
thawing time is the principal criterion that 
temperature at which the meat can be fi lleted 
governs selection of the system. Appearance, 
or cut by hand . Lower temperatures (e.g.,  − 5 
bacteriological condition, and weight loss are 
to  − 2 ° C) are acceptable for meat that is des-
important if the material is to be sold in the 
tined for mechanical chopping, but such meat 
thawed condition but are less so if the meat 
is  “ tempered ”  rather than thawed. The two 
is for processing. 
processes should not be confused because 
 The design of any thawing system requires 
tempering only constitutes the initial phase 
knowledge of the particular environmental or 
of a complete thawing process. In practice , 
process conditions necessary to achieve a 
tempering can be a process in which the tem-
given thawing time, and the effect of these 
perature of the product is either raised or 
conditions on factors such as drip, evapora-
lowered to a value that is optimal for the next 
tive losses, appearance, and bacteriological 
processing stage. In this section, methods of 
quality. 
raising the product temperature will be dis-
 
The process of freezing a high water 
- 
cussed. Tempering systems where the tem-
content material such as meat takes place  
perature of frozen product is lowered will be 
over a range of temperatures rather than at an 
covered in the tempering and crust - freezing 
exact point, because as freezing proceeds, the 
section. 
concentration of solutes in the meat fl uid 
 Thawing is often considered as simply the 
steadily increases and progressively lowers 
reversal of the freezing process. However, 
the freezing temperature. Thawing simply 
inherent in thawing is a major problem that 
reverses this process. 
does not occur in the freezing operation. The 
 Thawing time depends on factors relating 
majority of the bacteria that cause spoilage 
to the product and the environmental condi-
or food poisoning are found on the surfaces 
tions and include: 
118    Chapter 5
  1.   
  dimensions  and  shape  of  the  product, 
on the other hand, employ heat generation 
particularly the thickness,  
inside the product. There is no simple guide 
  2.   
  change  in  enthalpy,  
to the choice of an optimum thawing system 
(Table  5.2 ). A thawing system should be con-
  3.   
  thermal  conductivity  of  the  product,  
sidered as one operation in the production 
  4.   
  initial  and  fi nal temperatures,  
chain. It receives frozen material, hopefully, 
  5.   
  surface  heat  transfer  coeffi cient, and  
within a known temperature range and of 
  6.   
  temperature  of  the  thawing  medium.    
specifi ed microbiological condition. It is 
 
Thermal conductivity has an important 
expected to deliver that same material in a 
effect in thawing. The conductivity of frozen 
given time in a totally thawed state. The 
meat muscle is three times that of the thawed 
weight loss and increase in bacterial numbers 
material. When thawing commences, the 
during thawing should be within acceptable 
surface rises above the initial freezing point. 
limits, which will vary from process to 
Subsequently, an increasing thickness of 
process. In some circumstances (e.g., direct 
poorly conducting material extends from the 
sale to the consumer), the appearance of the 
surface into the foodstuff, reducing the rate 
thawed product is crucial; in others, it may 
of heat fl ow into the centre of the material. 
be irrelevant. Apart from these factors, the 
This substantially increases the time required 
economics and overall practicality of the 
for thawing. 
thawing operation, including the capital and 
 There are two basic methods of thawing: 
running costs of the plant, the labor require-
thermal and electrical . Thermal methods are 
ments, ease of cleaning, and the fl exibility of 
dependant upon conventional heat conduc-
the plant to handle different products, must 
tion through the surface. Electrical methods, 
be  considered.   
 Table 5.2.    Advantages and disadvantages of different thawing systems 
     
     
   ADVANTAGES  
   DISADVANTAGES  
  Conduction 
  AIR  
  Easy   to  install:  can  be 
 Very slow, unless high velocities and 
systems  
adapted from chill 
high temperatures are used, when 
rooms. 
there can be weight loss, spoilage 
 Low velocity systems 
and appearance problems.  
retain good appearance.  
  WATER  
  Faster  than  air  systems.  
  Effl uent disposal. 
 Deterioration in appearance and 
microbiological condition. 
 Unsuitable for composite blocks.  
  VACUUM - HEAT 
  Fast. 
  Deterioration  in  appearance. 
(VHT)  
 Low surface temperatures. 
 High   cost . 
 Very  controllable. 
  Batch size limited.  
 Easily  cleaned.