Meat quality of indigenous fat-tail Namaqua Afrikaner, Dorper and the South African Mutton Merino breeds

Burger, Alta (2015-03)

Thesis (M Social Work)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: This study investigated the carcass composition and yield, physical meat quality attributes, proximate composition and sensory profile of the indigenous, fat-tailed Namaqua Afrikaner (NA) breed and compared it to that of two commercially farmed meat breeds, i.e. the Dorper (D) and the South African Mutton Merino (SAMM). Two crossbred genotypes, namely the NA x D and the SAMM x D were also evaluated. NA lambs were compared at five months of age with the D and SAMM: with exception of the rib cut, the wholesale meat cuts of the NA contained a lower (P ≤ 0.05) percentage of meat than those of the D. Apart from the loin cut, the wholesale cuts of the NA were comparable (P > 0.05) with those of the SAMM. A lower percentage fat, but a higher percentage bone was recorded in all of the cuts of the NA (P ≤ 0.05). The same study was repeated with NA and D hoggets. Here the difference between the two breeds in physiological age could be observed. At an older chronological age the NA lean meat yield compared favourably with that of the D (P > 0.05). Percentage fat and bone yield of the NA relative to the D were recorded as being lower and higher, respectively (P ≤ 0.05). A comparison of the carcass characteristics, physical attributes and nutritional composition of the NA with that of the D, SAMM, NA x D and SAMM x D were conducted over a three year period (2010-2012). Breed differences were observed for slaughter weight, carcass weight, pH, subcutaneous fat depth, cooking loss and percentage moisture content (P ≤ 0.05) of the longissimus lumborum muscle. Attributable to production year, differences were observed in dressing percentage, cooking loss, Warner-Bratzler shear force and percentage moisture content (P ≤ 0.05). Overall the results of the NA compared favourably with that of the late-maturing SAMM. The intramuscular fat (IMF) content of the NA was significantly less than the purebred breeds (D, SAMM) and crossbred genotypes (NA x D, SAMM x D). No breed differences were observed for shear force (average 49.3 ± 0. 85 N), implying that despite having a lower IMF content (%), the tenderness of the meat of the NA were comparable to the commercial meat breeds. The sensory profile of the NA meat was compared with that of the D and NA x D cross. No significant differences were reported for lamb aroma; fatty aroma; overall lamb flavour; herbaceous bush-like flavour and aroma; initial and sustained juiciness; metallic taste and residue. The only sensory attribute that differed was tenderness (first bite) with NA having the least tender meat. Tenderness was also highly correlated to other sensory attributes: overall lamb flavour, initial and sustained juiciness, as well as the IMF content (%). It can thus be concluded that the overall sensory profile of the NA did not differ significantly from that of D, except for tenderness. Since the NA is an unimproved, indigenous breed, it is noteworthy that its meat was mostly comparable with that of the commercial breeds, where traditionally it was presumed inferior. Thus, future research regarding consumer acceptance, as well as investigation of the fatty acid profile of the meat, should be conducted. Further studies should also compare the breeds for production traits of economic importance to determine whether any breed has advantages in robustness and fitness above other breeds under challenging nutritional and climatic conditions.

AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die karkassamestelling en -opbrengs, fisiese vleiskwaliteitseienskappe, voedingswaarde en sensoriese profiel van ʼn inheemse, vetstert skaapras, die Namakwa Afrikaner (NA), te ondersoek en te vergelyk met vleisrasse waarmee kommersieel geboer word, naamlik die Dorper (D) en Suid Afrikaanse Vleis Merino (SAVM). ’n NA x D kruising en SAVM x D kruising is ook geëvalueer as deel van die studie. NA, D en SAVM lammers is op die ouderdom van vyf maande vergelyk vir karkasopbrengs. Met uitsondering van die ribsnit het die groothandelvleissnitte (boud, lende, skouer) van die NA ’n laer (P ≤ 0.05) persentasie vleis bevat as dié van die D. Benewens die lendesnit, was die groothandelsnitte van die NA vergelykbaar (P > 0.05) met dié van die SAVM. ’n Laer persentasie vet, maar 'n hoër persentasie been is in al die snitte van die NA (P ≤ 0.05) aangeteken. Dieselfde studie is met jaar-oud NA en D lammers herhaal. Op hierdie ouer kronologiese ouderdom was die verskil in fisiologiese ouderdom tussen die twee rasse duidelik sigbaar. Op ’n ouer ouderdom vergelyk die maer-vleisopbrengs van die NA gunstig met dié van die D (P > 0.05). Weereens was die opbrengs van die persentasie vet en been in die NA-karkas opgeteken as onderskeidelik laer en hoër. Die karkaseienskappe, fisiese vleiskwaliteit en die voedingswaarde van die NA, D, SAVM, NA x D en SAVM x D is oor ’n tydperk van drie jaar nagevors (2010-2012). Rasverskille is waargeneem vir slaggewig, karkasgewig, pH, onderhuidse vetdikte, kookverlies en die persentasie voginhoud (P ≤ 0.05) van die longissimus lumborum (LL) spier. Verskille waargeneem in die uitslagpersentasie, kookverlies, Warner-Bratzler skeurkrag (instrumentele sagtheid) en die persentasie voginhoud (P ≤ 0.05) was toeskryfbaar aan die produksiejaar. In die algemeen het die resultate van die NA gunstig vergelyk met dié van SAVM, ook ’n ras wat gereken word as laat-volwasse. Die intramuskulêre vetinhoud (IMV) van die NA was aansienlik minder as dié van beide die suiwer rasse (D, SAVM) en die kruisgeteelde genotipes (NA x D, SAVM x D). Geen rasverskille is aangeteken vir skeurkrag (gemiddeld 49.3 ± 0. 85 N) nie. Dit impliseer dat, ondanks 'n laer IMV inhoud (%), die instrumentele sagtheid van NA vleis gunstig vergelyk met dié van die kommersiële vleisrasse. Die sensoriese profiel van die NA vleis het gunstig vergelyk met dié van die D en NA x D kruis. Geen beduidende verskille is vir lam-aroma; vetaroma; algehele lamgeur; kruidagtige bossiegeur en -aroma; aanvanklike en volhoubare sappigheid; metaalsmaak en residu gevind nie. Die enigste sensoriese kenmerk waarin ’n rasverskil gevind is, is aanvanklike sagtheid. Die vleis van die NA was die taaiste. Sagtheid was ook hoog gekorreleer met ander sensoriese eienskappe: algehele lamgeur, aanvanklike en volhoubare sappigheid, sowel as die IMV inhoud (%). Daar is dus tot die gevolgtrekking gekom dat die algemene sensories profiel van die NA nie beduidend van dié van die D en NA x D verskil het nie. Aangesien die NA 'n onverbeterde, inheemse ras is en tradisioneel as minderwaardig beskou word, is dit noemenswaardig dat die vleis daarvan in die algemeen gunstig vergelyk het met dié van die kommersiële rasse. Dus, toekomstige navorsing kan fokus op verbruikersaanvaarding van die vleis. Verder kan navorsing op die vetsuurprofiel van die vleis gedoen word. Met studies waarin die rasse vergelyk word vir produksie-eienskappe van ekonomiese belang, sal bepaal kan word of die inheemse ras voordele inhou in terme van robuustheid en fiksheid onder beperkende voedingsomstandighede en ongunstige klimaatstoestande.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/96630
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