Quality and Grading of Carcasses of Meat Animals

241 Pages·1995·31.61 MB·\241

by  S. Morgan Jones (Author)

Quality and Grading
of
Carcasses of Meat Animals
Edited by
S.D. Morgan Jones, Ph.D.
Agriculture and Agri-Food Canada
Research Centre
Lacombe,Alberta
Canada
CRCPress
BocaRaton New York London Tokyo
Library ofCongress Cataloging-in-Publication Data
Qualityand gradingofcarcasses ofmeatanimals/editedbyS.D.
MorganJones,
p. cm.
Includesbibliographicalreferences and index.
ISBN 0-8493-5023-9
1. Meat—Quality. 2. Meat— Grading. 3. Meatindustryandtrade­
-Quality control. I. Jones, Stephen DavidMorgan.
TS1962.Q35 1995
664'.907— dc20 94-37142
CIP
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PREFACE
In many countries there is presently considerable interest in factors that influence
the composition and quality of meat and in technologies that can predict these
attributesinwhole carcasses.Thequalityand composition ofmeatis influenced by
theproduction, marketing,and postmortem periods. However,itis consideredthat
production factors are moreimportantfordeterminingthecomposition ofthe meat,
while the marketing and postmortem periods have a major bearing on the visual
appearance andultimateeatingexperiencefortheconsumer. Chapters 1to 3review
the main factors influencing the composition andquality ofmeat. Meatquality is
assessed by a wide variety of procedures and it is often difficult to compare
researchresultsfromdifferent countries. Chapter 4providesabroadoutlineofthe
most common subjective and objective procedures for the assessment of meat
quality. Sincered meat has oftenbeen implicated as a highersource ofdietary fat
than white meat, Chapter 6 reviews the relationship of meat composition to its
resulting consumerpalatability. Chapters 5and 7coverthe new technologies that
may have potentialto provide rapid estimates of meat composition, carcass yield,
and meatquality from measurements madeon the intact carcass, while Chapter 8
reviews the development of commercial grading or classification schemes on a
world-wide basis. An essential part of any measurement system is the ability to
identify the animal through slaughter and processing. Current progress made on
electronic identification and on some of the larger field trials that have been
conducted is provided in Chapter 9. The final chapter in the book (Chapter 10)
considers existing technologies for the evaluation of carcasses and attempts to
project how these technologies may be adapted for future use in commercial
grading or classification schemes.
The late Professor Leon Rubin of the University ofToronto prompted me to
gather thematerial inthisbookandIamgrateful to himfor hisinitialguidanceon
this project. My thanks are also extended to all the authors who contributed
chapters and for their patience while a final draft was being prepared. I am also
indebted to IreneThaubergeratthe LacombeResearchCentreforcoordinatingthis
project and keeping the extensive correspondence in order.
S. D. Morgan Jones
Editor
EDITOR
StephenMorganJones,B.Sc.,M.Sc., Ph.D., isDirectoroftheLacombeResearch
CentreinAlberta, Canada. Heobtainedhistraining at theUniversitiesofWalesand
Reading, receiving the B.Sc. (Hon.) degree in 1972, M.Sc. (Reading) and Ph.D.
(Reading) degrees in 1973and 1977,respectively. He servedas a Research Asso­
ciateat the UniversityofAlbertain Edmonton from 1977to 1979; as Assistant and
Associate Professor of Meat Science at the University of Guelph from 1979 to
1984; as Head ofMeat Research at the Lacombe Research Station from 1985 to
1994; and in 1994 he assumed his present position.
Dr. StephenMorgan Jonesisa memberoftheAgriculturalInstituteofCanada,
theCanadian,Americanand BritishSocietiesofAnimalScienceandtheCanadian
andAmericanAssociations ofMeatScience.Hewas formerly thePresidentofboth
theCanadian Society ofAnimal Science andtheCanadianMeatScienceAssocia­
tion. He is currently the Editorofthe CanadianJournalofAnimalScience and a
memberoftheEditorialBoardofMeatScience. Heis anAdjunctProfessoratthe
University of Alberta and has been the recipient of research grants from the
National Science and Engineering Research Council, the Provinces of Alberta,
Manitoba, and Ontario, the Canadian Meat Council, the Canadian Pork Council,
theCanadianCattlemen'sAssociationandvariousother industrygroups. Hiswork
has been recognized by industry through receipt ofthe Science and Technology
Award by the Canadian Meat Council, the young Scientist and Canada Packers
Awards by the Canadian Society of Animal Science and an Achievement Award
from the Minister of Agriculture and Agri-Food Canada.
Dr. Stephen Morgan Jones isthe authorof over 100reviewed papers and 150
technical articles. His currentresearchinterests relateto the objective measurement
ofcarcass characteristics and meat quality.
CONTRIBUTORS
J. L. Aalhus, Ph.D. R. Robinson, B.Sc. (Agr.)
Agriculture and Agri-Food Canada Agriculture and Agri-Food Canada
Meat Research Section Food Production and Inspection
Lacombe Research Centre Branch
Lacombe, Alberta, Canada Meat and Poultry Products Division
Nepean, Ontario, Canada
J. C. Forrest, Ph.D.
A. L. Schaefer, Ph.D.
Animal Sciences
Agriculture and Agri-Food Canada
Purdue University
MeatResearch Section
West Lafayette, Indiana
Lacombe Research Centre
Lacombe, Alberta, Canada
S. D. Morgan Jones, Ph.D.
Agriculture and Agri-Food Canada H. J. Swatland, Ph.D.
Meat Research Section Department ofAnimal and Poultry
Lacombe Research Centre Science
Lacombe, Alberta, Canada University ofGuelph
Guelph, Ontario, Canada
A. C. Murray, Ph.D.
P. D. Warriss, Ph.D.
Agriculture and Agri-Food Canada
Division ofFood Animal Science
Meat Research Section
School ofVeterinary Science
Lacombe Research Centre
University of Bristol
Lacombe, Alberta, Canada
Langford, Bristol, United Kingdom
M. A. Price, Ph.D. J. D. Wood, Ph.D.
Department ofAgricultural Food Division ofFood Animal Science
and Nutritional Science School ofVeterinary Science
University ofAlberta University ofBristol
Edmonton, Alberta, Canada Langford, Bristol, United Kingdom
CONTENTS
Chapter 1
Antemortem Factors Influencing the Yield and Quality ofMeat from
Farm Animals ...................................................................................................1
Paul D. Warriss
Chapter 2
New Techniques to Reduce Fatness in Farm Animals.........................................17
Allan L. Schaefer
Chapter 3
Postmortem Effects on the Appearance and EatingQuality of Meat................ 51
Jennifer L. Aalhus
Chapter4
The Evaluation ofMuscle Quality ...... 83
Austin C. Murray
Chapter 5
Electronic Assessment ofMuscle Quality............................................................109
Howard J. Swatland
Chapter 6
The Influence ofCarcass Composition on Meat Quality.................................131
Jeff D. Wood
Chapter 7
New Techniques forEstimation ofCarcass Composition................................ 157
John C. Forrest
Chapter 8
Development ofCarcass Grading and Classification Systems......................... 173
Mick A. Price
Chapter 9
Electronic Identification ofAnimals and Carcasses ......................................201
Richard Robinson
Chapter 10
Future Directions for Carcass Assessment.................... 215
Stephen D. MorganJones
Index 229
Chapter 1
Antemortem Factors Influencing the Yield
and Quality of Meat from Farm Animals
P. D. Warriss
CONTENTS
I. Introduction.......................................................................................................1
n. Live and Carcass Weight Loss........................................................................2
A. Carcass Shrinkage in Pigs.........................................................................2
B. Shrinkage in Ruminants.............................................................................3
C. OtherConsiderations Relating to Inanition.............................................5
HI. Marketing and Lean Meat Quality..................................................................5
A. The Prevalence ofPSE andDFD Pork...................................................6
B. Effects ofTransport and Lairage on Pork Quality................................6
C. Controlling Feed Withdrawal Periods.....................................................7
D. Practical Concerns with the Handling ofPigs.......................................7
E. Marketing Effects on Lean Meat Quality in Ruminants.......................8
IV. Measures to Counteract Undesirable Consequences of
Marketing Procedures.....................................................................................10
V. Conclusions......................................................................................................11
References...................................................................................................................12
I. INTRODUCTION
The way wehandle animals antemortem has been highlighted in recent years for
two reasons. First,in an increasinglycompetitivemarket and with theemphasison
quality of the final product, the economic losses caused by poor handling are
becoming more widely realized. Second, consumers in many countries have be­
comemoreawareofthe ethics ofmeat production. They want theirmeat produced
in ways thattake accountofanimal welfare. Indeed, welfare-friendlyproducts may
commanda premiumprice. Antemortemhandlingisseenas justasmuchapart of
this concern for the animal’s welfare as are the husbandry practices followed
during rearing.
The slaughteringindustry inmany countriesisbecomingcentralizedinto fewer,
largerplants. Marketing times and the distances animals must travel to slaughter
are therefore likely to have increased. This is particularly true if stock are sold
through live auctions or are exported so the marketing process includes several
stages of assembly and transport. In this regard the introduction of computer
auctions, where animalsare sold without theneedtotake themtocentral collection
points, may have welfare and quality benefits if the duration and severity of
handlingare reduced.Anotherproblem is that largerslaughterplants oftenoperate
at higher line speeds than small plants. The need to move and process animals
0-8493-5023-9/95/$0.00+$.50
©1995byCRCPress,Inc. 1
2
\
Liveweight loss
\
Carcass&offalweight loss Urine& faeces
lossofprotein lossof water
andfat
mobilisation normalevaporation,
forenergy sweating &pantingfor
thermoregulation
Figure 1 Componentsofweightloss.
rapidly also inevitably lends to potentially more stress in the period immediately
before slaughter.
Even when carried out with duecare and consideration, themarketing process
is inherently stressful. Animalsareremovedfromtheirhomeenvironment, loaded
and unloadedfromtransportvehicles, subjectedto oftenlongjourneys, andheldin
unfamiliarsurroundings. They may beexposedto various stressors such asnoise,
unfamiliar smells, deprivation offood and water, vibration, extremes oftempera­
ture, breakdown ofsocial groupings, close confinement, and overcrowding. How
the animal responds to these stresses can lead to reductions in carcass yield and
meat quality. Yield is reduced by losses of live and potential carcass weight
(“shrinkage”)causedby combinationsofinanitionandhandling stress. Leanmeat
quality can be affected through the production of pale, soft, exudative (PSE) or
dark, firm, dry (DFD) meat and also in less well understood ways that influence
eating quality.
II. LIVE AND CARCASS WEIGHT LOSS
Lossofliveweightcanbepartitionedinto lossofurineandfeces and loss ofcarcass
and offal (Figure 1). Loss ofpotential carcass yield could be caused both by loss
ofprotein and fat and by loss of water (dehydration). Ifan animal is deprived of
food (fasted) it will mobilize body tissues to provide energy for maintaining the
vital functionsofthebody. More loss is possibleiftheanimalis subjectedto greater
energydemands, suchas thoseneededtomaintainbalanceorto thermoregulatein
transport. Thermoregulation mayinvolve greaterlossofbodywater throughsweat­
ing or panting. In longer transport particularly, animals can become dehydrated.
A. CARCASS SHRINKAGE IN PIGS
Live weightbeginsto be lostalmostimmediately afterfeedwithdrawal from pigs
at a rate of between about 0.12 and 0.20% per hour.13A large part of this loss,
particularly initially, isattributableto lossofurine andfeces. It is less clearwhen
3
carcass weightlossbegins,butthisisprobablybetween about9and 18hafterthe
last meal, reflecting therelativelyrapidpassageoffood through the pig’s gut. Most
recent studies have foundratesofcarcass loss, determinedoverfasting periodsof
48 h or more, tovarybetween0.06and 0.14%per hour. Wherepigs havenotbeen
given access to waterduring the whole period offasting the rate ofloss tends to
be higher. Overall, an average working figure of 0.1% per hour would appear
reasonable. Carcass weight loss accounts for up to about one third of total live
weight loss overthe first 24 hof fasting and up to one half between 24 and 48 h.
Although the rates ofcarcass loss appear small they result in significant eco­
nomic lossesundercommercial conditions. Fora90-kgpig(live),a loss ofbetween
0.8 and 1.6kgofpotential carcass yieldmight be expected afterdeprivationoffood
for 24 h. This is equivalent to the loss ofvalue ofmore than 1pig for every 100
marketed. That the loss in carcass weight is largely attributable to loss of protein
and, toa lesserdegree, fat,ratherthan lossofwater, issupportedbyevidence that
the reduced yield is maintained after curing.45
Jones et al.6showed that there were no differences in the effects offasting on
thecarcassyield ofpigsofdifferentstress-susceptibility genotypes.Theinfluence
of ambient temperature during fasting is not clear. High temperatures could in­
creaseweight lossby greater lossofmoisture fromtherespiratorytract, especially
through panting. Groups of pigs can tolerate low temperatures to some degree by
huddling together, thus modifying their immediate microclimate and reducing
body heat loss.
How the othermajor antemortem stress, transport, affects carcass yield is less
clearbecausefew studieshaveexaminedit in isolation.In anexperiment conducted
insummer, transportfor 1h resultedin anonsignificantloss of0.6%carcassyield,
while a journey lasting 6 h reduced it by 2%.7The pigs given the longjourney
showed evidence of dehydration, suggesting that, in contrast to those caused by
fasting, transportyield lossesarealsoattributable to tissue waterlosses. Mayeset
al.8 transportedpigsabout 400milesfollowedby periodsoffasting from24to72h.
Transport reduced carcass yield by between 1.0 and 1.9 killing out percentage
units. There is some informationontheeffectsofvery long transporttimes (29 h)
on pigs exported from The Netherlands to Italy.9Carcass weight was reduced by
4 kg, mainly due to water loss.
B. SHRINKAGE IN RUMINANTS
Becauseoftheirproportionallylargerguts and thefactthatthe rumenactsas a store
ofnutrientsand water, larger ruminantsin particular aregenerally less susceptible
thanpigstoinanition. Thegut contents ofadult cattlecanaccount forover 20%of
the live weight and form a majorcomponentoflive weight losses overthe initial
24h offood deprivation.Gut fill is largerinanimals onhighroughagepasture than
in thosefedgrain diets and inanimals that haverecently drunk. Previousdietand
access to water are therefore important factors influencing the patterns of live
weight loss in ruminants. Even if food is offered there is evidence that under
conditions ofstresssomeruminantsmay bereluctantto takeit, and this may extend
effectivefastingtimesunder commercialmarketingconditions. Iffood is unavail­
able, waterconsumption may also be reduced to very low levels in sheep.
Results from various studies on sheep1011have indicated average live weight
lossesrangingfrom0.09to0.34%per hour, andratesofcarcass loss varyingfrom