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tohaveaccesstoregularsuppliesofnourishingfoodandtosufferlessfromneonatallosses.Improvedbreedsareearlymaturing;alsotendtogivegreatercarcassyieldthansemi-wildbreedsbecauseoftheirincreasedleveloffatness,higherpercentageoffatinthecarcassthanlatermaturing.Moreover,thesubcutaneousappearstoincreaseandmoredevelopedwhicharerelatedtotheoverallsize.
Whyaremeatsimportant?
Meathasformedpartofthedietasasourceofproteinsinceprehistoricandtedevelopmentofhuntingskills.
Meathashighbiologicalvalueof0.75comparedtoothersourcesofproteinsucaswheat,whichonlyhas0.50.
Meathashighsatietyvalueorhighfeelingofsatisfaction.Whatarethecompositionalandnutritivevaluesofmeat?
Meatisconsidered,justifiably,asahighproteinfood(Table1).Ofthetotalitrogencontentofmuscle,95%isprotein+5%peptides,aminoacidsandothercompounds
Meatproteinshavesimilardigestibilitywiththatmilkandeggsandhighercomaredtoplantproteins(78-88%)
Meathaslipidcontentsohasdietarysignificanceasitrelatestoenergyandbesity
Meatcontainscholesterolandsaturatedfattyacids
Meathashighbiologicalvaluecomparedtosomeproteinsources
- MeatProtein = 0.75- WheatProtein = 0.50- WheatFlour = 0.52
Table1.thecompositionofleanmuscletissueofmeatanimals(%)Species
Water Protein Lipid AshBeef 70-73 20-22 4-8 1.0Chicken 73-75 20-23
4-7 1.0Lamb 73 20 5-6 1.4Pork 68.70 68-70 9-11 1.4
Whatisbiologicalvalueandnetproteinutilization?Theseareparametersofproteinquality:BV=INUN-FN
IN-FN
Where: IN = NitrogenintakeUN = UrinaryNitrogenOutputFN =
FecalNitrogenOutput
NetProteinUtilizationistheratioofnitrogenretained,totalnitrogenintake,andistheninfluencedbyBVanddigestibilityoftheprotein.
Whataresomeproblemsrelatedtomeatconsumption?
Theroleofmeatshould,however,beplacedinperspective:
MeatconsumptionamongAmericansiscertainlyhighandlargelyunlimitedbyfinncialconstraints
Thereisalsoatendencytoconsumptionofhighfatproductssuchasburgers
Meatconsumptionisonlyapartoftheequationsincenon-meatenergyintakeisalsohighandcontributestothelayingdownoffatasalongtermreserve
Meatcontainscholesterolandsaturatedfattyacids,apredisposingfactorstoeartdiseases
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- Leanmeat = 65-75 mg/100g- Kidney = 400 mg/100g- liver = 430
mg/100g
Lowenergyrequirementforsedentaryworkandover-alldietaryhabitsandlifetyleareunderlyingcausesofobesityHowthetypesofmeatare,differindegreeofsaturation?
Beefandmuttonhavethehighestfollowedbyporkandthenchicken.
Howdoesthedegreeofunsaturationbealtered?
DegreeofunsaturationcanbealteredbymeansofsupercriticalCOextraction.Thisistechnicallybutnotcommerciallyfeasible.
GuideQuestions:
TrueorFalse
1.
Thedevelopmentofhugemeatindustrywasfastbecauseofpopularityofmeatasafood.2.
Thechangingconsumersfoodrequirementsinfluencedthedirectionoftheindustry.3.
Dogsareincludedamongthesourcesofmeat.4.
Meathaslowsatietyvaluesoonedoesnotfeeleasilyhungryafterameat-meal.
5.
Domesticationhasapositiveeffecttotheover-allqualityofthemeat.6.
Meatisrichinfatssohashighcaloricvalue.7.
DegreeofsaturationcaneasilybealteredbymeansofsupercriticalCOextraction.8.
Meatislimitedtoanimalsources.9.
Chemicallaboratorieswereestablishedearliertotakecareoftheneedsmeatindustry.10.
Meatproteinshavesimilardigestibilitywiththatofmilkandeggs.
Enumeratetheff:
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1. Stagesofdomestication2. Importanceofmeat3. Sourcesofmeat
ExercisesandActivitiesfortheLesson1I.
Thestudentswillconductaninterviewtotheslaughterhousesownersregardingtheirfarmmeattechnologypracticesandcompareittothepastfarmpractices.Basedonthegathereddata,thestudentswillpredictthefutureadvancementinmeatprocessingtechnology.II.
SensoryTestThestudentswillbringmeatsamplestakenfromthelocalmarket(freshcarcass,frozenandopenairventilatedcarcass)about.50kilogramsineverysamplea.
Distinguishthecarcassqualitybythefollowingstandards:TexturalcharacteristicsCarcasscolor-
OdorcharacteristicsTaste(cooked)-III.
ThestudentswillconductanocularobservationtothevariousequipmentandmaterialsbeingusedbythelocalSlaughterhouse.Classificationofslaughterhouseaccordingtostandard.Nameofslaughterhouse
InternationalAndlocalmarket(AA) Nationalmarket(A)
Provincialmarket(B) Localmarket(C)1234
IV.
Thestudentswillvisitvariousstallsandpublicmarketinthelocalcommunityanddeterminethefollowing:Typesofmeat
Demandin2010(%) Supplyin2010(%)
DemandGap(%)porkbeefcarabeefmuttonPoultrymeatNote:thestudentswilldetermine/gatherthedataonthetotalpopulationofthecommunity.
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Lesson2MuscleandAssociatedTissues
Objectives:Attheendofthislesson,thestudentshouldbeableto:
1. Discussthedifferentmuscletypeandassociatedtissues;2.
Understandthegrowthanddevelopmentofmuscles;3.
Outlinethemusclecomponentsandtheirmechanismofcontraction.Whatismeatstructurallycomposedof?
Meatiscomposedprimarilyofmuscles,plusvariablequantitiesofallthetypesofconnectivetissues,adipose(fatty)aswellassomeepithelialandnervoustissues.Boneisanessentialpartofthemeatanimal.
Whatareassociatedconnectivetissues?
Surroundingthemuscleasawholeisasheathofconnectivetissueknownastheepimysium:fromtheinnersurfaceofthelatter,septaofconnectivetissuepenetrateintothemuscle,separatingitsessentialstructuralelements,themusclefibersintobundles.Theseparatingseptaconstitutestheperimysium,whichcontainsthelargerbloodvesselsandnerves.Fromtheperimysiumafineconnectivetissuearoundeachfibercalledtheinwardstosurroundeachmusclefibe
r.Theconnectivetissuearoundeachcalledtheendomysiumofreticulinisanamorphous,nonfibroussheathandassociatedwithfineconnectivetissuefibers.Astructure,referredtoasthebasementmembrane,linksthecollagenousfibersoftheendomysuimtothecellmembrane.Onlyabout40percentofthedryweightofthebasementmembraneiscollagen,theremainderconsistingofcomplexpolysaccharides,proteoglycansandglycoproteins.
Howaremusclefibersattachedtothebone?
Musclefibersdonotthemselvesdirectlyattachtotheboneswhichtheymoveorinrelationtowhichtheirforceisexerted;theendomysium,perimysiumandpimysiumblendwithmassiveaggregatesofconnectivetissue(ortendons)andtheseattachtotheskeleton,buttheprecisemodeofconnectionbetweentheco
ntractileproteinsandtendonisnotyetclear.Microscopicexaminationoftendonsshowsthattheconstituentbundlesofcollagenfibrilshaveregularcrimpatintervalofca.100um.Itseemspossiblethatthisfeaturepermitsthecollagentotakeuptheinitialshockofmovementbystraighteningthecrimpbeforethetendonsustainsthefullload.Theultimatetensilestrengthoftendon,atanextensionof1015percent,isca.1lOONnm~comparedwithca.220Nnmforaluminum(Baley,1989).
Connectivetissueincludesformedelementsandanamorphousgroundsubstanceinwhichtheformedelementsarefrequentlyembedded.Thelatterconsistofthefibersofcollagen,whicharestraight,inextensibleandnon-branching;andofelastin,whichareelastic,branchingandyellowincolor.
Whataremuscletissues?
Muscletissues,theleanportionofthemeat,arebundlesoffibersormuscleheldtogetherwithconnectivetissues(Fig.1).Therearetwotypesofconnectivetissuescollagen,whichiswhite,andelastic,whichisyellow.Collagencanbetenderizedbypropercooking.Ifcookedforalongtimeatalowtemperaturebymoistheat,itgraduallybreaksdownandturnstogelatinandwater.Meatcutsthatarehighincollagen,suchasbrisket,plateandchuck,arethereforecookedbymoistheatmethods.Meatcutsthatarelowincollagenandhavefine
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actionsinthemuscle
Severalenzymesconsistofmorethanonemolecularspecies(isozymes)
Theproportionofeachglycolyticenzymeswhichisboundincreaseonstimulatioofglycolysis(e.g.electrical)anddecreasewhensuchstimulationceases
Theenhancedbindingonstimulationtoactivityisespeciallymarkedinrespectofphosphofructokinase,triosephosphatedehydrogenase,aldolase,phosphopyruvatehydrataseandphosphospyruvatekinase
Thebindingofaldolaseandoftriosephosphatedebydrogenase
