Proportional yields and processing of pork derived from different halothane hyperthermia pig genotypes

Fisher, Peter Philip (1998-12)

Dissertation (Ph.D. Agric.) -- University of Stellenbosch, 1998.

Thesis

ENGLISH ABSTRACT: The carcass and meat quality characteristics of three halothane genotypes in pigs were evaluated. Sixty crossbred Landrace x Large White pigs (NN = 25, Nn = 19, nn = 16) of ± 86 kg live weight were slaughtered, the carcasses chilled for 24 h at 2°C, certain carcass and meat quality traits determined and the shoulder and leg cuts deboned and devided into primal cuts. Least squares (LS) means for dressing percentage of the Nn genotypes was higher (P < 0.05) than that of the NN and nn genotypes. LS means for carcass length was highest (P < 0.05) for carcasses derived from the nn genotype. The LS means calculated for several measurements on the split carcasses (midline fat measurements) and cross sections between the 2nd and 3rd last thoracic vertebrae relating to fat depositioning (45 mm from the midline) and lean depositioning (eye muscle width, depth and area) provided significant evidence that the nn genotype yielded leaner carcasses than Nn and NN genotypes. Fitting prediction equations to some of the these measurements to calculate LS means for predicted lean yield confirmed that nn genotypes yielded carcasses with less fat and more lean. Further dissecting of selected cuts (shoulders and legs) also showed that the LS means for bone, fat and lean yield from nn genotypes were more desired than those from the other two genotypes, with probabilities varying from P > 0.05 to P -< 0.001. It was also demonstrated that the LS means of all subprimal cuts from the legs (topside, silverside, thickflank and rump) expressed as a percentage of cold carcass weight were higher for carcasses originating from the nn genotype (P < 0.05). This could be ascribed to the higher LS means for leg weight (P < 0.05) originating from the nn genotype. However, when meat quality traits were compared the shortfall of the nn genotypes became evident. LS means for pILs (P < 0.001), pH24 (P < 0.05), drip loss (P < 0.001) and reflectance values (P < 0.05) differed and were inferior for this genotype. The backs and legs were used to prepare cured, smoked bacon and canned hams. Comparison of LS means revealed the following: initial gain in pumped weight was significantly higher (P < 0.001) for the NN and Nn genotypes compared to the nn genotypes. Similarly, the total gain in bacon yield (finished product yield) was the highest for the Nn (11.5%) and NN genotypes (1O.0%), significantly higher (P < 0.05) than the bacon produced from the backs of the nn genotypes (3.4%). Differences between sexes were not significant. Canned hams (without added phosphate) produced from the NN genotypes had a significantly (P < 0.001) lower percentage cooking loss (27.92%) compared to that of the Nn (30.12%) and nn genotypes (31.14%), which did not differ. Addition of phosphates (0.3% on final product) had a similar response, with the hams produced from the NN genotype having 13.75% cooking loss, significantly lower (P < 0.001) than the Nn (16.87%) and nn genotypes (17.73%). Results for the two types of fresh sausage manufactured from the meat of the different genotypes (with rusk, without rusk) indicated that for the sausage without rusk that the NN genotypes (15.7%) had lower total moisture losses (P < 0.05) compared to the nn genotypes (18.9%), with Nn intermediate (17.4%). The treatment with rusk addition did not differ significantly between genotypes (NN = 12.6%, Nn = 13.0, nn = 14.2%), indicating that some of the disadvantages may be overcome by processing technique. Taste panel evaluation of the fresh sausage made without rusk indicated no differences between genotypes when evaluated for juiciness. In an emulsion type sausage the smoking and cooking losses during manufacturing of the product indicated that the sausage manufactured from the meat of the nn genotype (12.47%) had significantly (P < 0.05) higher losses than that from the Nn genotype (1l.31 %), with NN genotype intermediate (12.35%). The results from this investigation suggest that the presence of the halothane gene is associated with decreased fresh meat and processing properties (lower water holding capacity, reflected by yield or total loss and higher reflectance values) in certain products. This leads to inferior quality in finished products as well as deminished financial returns for processors.

AFRIKAANSE OPSOMMING: Die karkas-, vleiskwaliteit en prosesseringseienskappe van die drie halotaangenotipes in varke is geevalueer. Sestig Landras x Grootwit varke (NN = 25, Nn = 19, nn = 16) is op ± 86 kg lewende gewig geslag, die karkasse vir 24 uur verkoel teen 2 °C en sekere karkas- en vleiskwaliteitseienskappe bepaal. Kleinste vierkant (KKG) gemiddeldes bereken vir uitslagpersentasie het aangedui dat die Nn genotipes 'n hoer gemiddelde (P < 0.05) het as beide die NN en nn genotipes. KKG gemiddeldes vir karkaslengte was die hoogste (P < 0.05) vir die nn genotipes. KKG gemiddeldes vir verskeie mates op die halveerde karkas (mediale vetdiktes) asook vet- en spiermates (oogspierwydte, -diepte, en -oppervlak) lateraal (45 mm vanaf middellyn) van die werwelkolom tussen die 2de en 3de laaste torakswerwel het betekenisvolle bewys gelewer dat die nn genotipe karkasse met 'n hoer maervleisinhoud het as die NN en Nn genotipes. Voorspellingsvergelykings vir enkele van hierdie mates waarmee die KKG gemiddeldes bereken is het bevestig dat die nn genotipes karkasse met minder vet en meer maervleis gee. Disseksie van geselekteerde snitte (skouers en boude) het ook aangedui dat die KKG gemiddeldes vir been-, vet- en maervleisopbrengs meer voordelig was vir die nn genotipe, met waarskynlikhede wat gewissel het van P > 0.05 tot P < 0.001. Dit is ook gedemonstreer dat dat die KKG gemiddeldes vir al die maervleissnitte (binneboudstuk, dy, diklies en kruisstuk), bereken as 'n persentasie van koue karkasmassa, hoer (P < 0.05) was vir die karkasse atkomstig van die nn genotipe. Dit kan toegeskryf word aan die hoer KKG gemiddelde vir boudmassa (P < 0.05) van die nn genotipes. Vergelyking van KKG gemiddeles vir vleiskwaliteitseienskappe het egetr die tekorte van die nn genotipe uitgewys. KKG gemiddeldes vir pIL5 (P < 0.001), pH24 (P < 0.05), drupverlies (P < 0.001) en refleksiewaardes (P < 0.05) het verskil en was swakker as die KKG gemiddeldes van die ander genotipes. Die hamme en lendes atkomstig is gebruik vir die vervaardiging van gepekelde rugspek en geblikte hamme. Aanvanklike gewigstoename, na pekelinspuiting, was betekenisvol hoer (P < 0.05) vir die NN (15.2%) en Nn genotipe (14.9%), indien dit vergelyk word met die nn genotipe (8.9%). Soortgelyk was die totale toename in spekopbrengs vir die NN (10%) en Nn genotipe (11.5%) betekenisvol hoer (P < 0.05) indien dit vergelyk word met die nn genotipe (3.4%). Die geblikte hamme (sonder bygevoegde fosfaat) atkomstig van die NN genotipe het 'n betekenisvol laer (P < 0.001) persentasie kookverlies (27.92%) gehad vergeleke met die Nn (30.12%) en nn genotipe (31.14%), wat nie ,an mekaar verskil het nie. Die byvoeging van fosfate (0.3% in die finale produk) het 'n soortgelyke respons meegebring. Die NN genotipe het betekenisvol (P < 0.001) laer kookverliese (13.75%) gehad vergeleke met die Nn (16.87%) en nn genotipes (17.73%). Die resultate van die twee tipes wors (met graan en sonder graan) wat uit die vleis afkomstig van drie genotipes vervaardig is het aangedui dat, vir die wors vervaardig sonder bygevoegde graan, die NN genotipe betekenisvol (P < 0.05) minder vog verloor het (15.7%) vergeleke met die nn genotipe (18.9%). Die Nn genotipe het 'n intermediere waarde vir vogverlies gehad (17.4%). Die byvoeging van graan het kleiner verkille tussen genotipes (NN = 12.6%, Nn = 13.0%, nn = 14.2%) tot gevolg gehad, met geen betekenisvolle verskille tussen genotipes. Proepaneelevaluering van die wors (vervaardig sonder graan) het geen verskille tussen genotipes ten opsigte van sappigheid uitgelig nie, maar die wors met bygevoegde graan het het weI groter verskille getoon. Die wors vervaardig van die nn genotipe was die sappigste, met die NN genotipe die minste sappig en Nn intermedier. Vergelyking van berokings- en kookverliese tydens die vervaardiging van 'n emulsieproduk (vienna) afkomstig van die drie genotipes het op 'n betekenisvolle verskil (P < 0.05) tussen die Nn (1l.31 %) en nn genotipe (12.47%) gedui, met NN intermedier (12.35%). Die resulate van hierdie studie stel voor dat die teenwoordigheid van die halotaangeen geassosieer is met 'n afname in beide vars vleiskwaliteit en prosseseringseienskappe van sekere produkte (lae aanvanklike pH, bleek kleur, verminderde waterbindingsvermoe, lae finale produkopbrengste). Dit gee aanleiding tot 'n daling in produkkwaliteit en het gevolglik 'n negatiewe finansiele uitwerking op die vleisprosesseerder. Die aanbeveling is dus sterk teen die gebruik van die halotaangeen in enige kommersiele varkproduksiestelsel wat gemik is op die verskaffing van vleisprodukte van hoogstaande gehalte.

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