Profiling the meat quality of blue wildebeest (Connochaetes taurinus)

Van Heerden, Aletta Margaretha (2018-03)

Thesis (MScAgric)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: The aim of this study was to provide baseline data on the overall yield and quality (physical attributes, chemical composition, sensory profile and optimum aging period) of six muscles [Longissimus thoracis et lumborum (LTL), Biceps femoris (BF), Semimembranosus (SM), Semitendinosus (ST), Infraspinatus (IS) and Supraspinatus (SS)] of blue wildebeest bulls (Connochaetes taurinus) culled from an extensive and semi-extensive production system in South Africa. There is a need for this information due to the lack of scientific information on the meat quality of this species and the effects of various extrinsic and intrinsic factors thereupon. In the first trial, eight blue wildebeest bulls were culled from a semi-extensive production system and eight from an extensive system where ages were matched and divided into adult and sub-adult treatments. Semi-extensive wildebeest showed to have the potential to increase carcass yield by having significantly higher undressed carcass weights (208.2 ± 11.14 kg), carcass weights (112.1 ± 6.38 kg) and dressing percentages (53.8%) than the extensive (168.8 ± 14.59 kg, 84.9 ± 7.55 kg and 50.2%, respectively). Semi-extensively raised blue wildebeest also showed higher weights for external and internal offal parts as well as producing significantly (p<.0001) higher total muscle yields (19.8 ± 0.91 kg) than the extensive system (14.8 ± 1.22 kg), with differences being associated with the loin and hindquarter muscles and not the forequarter muscles. Differences in the physical meat quality attributes of blue wildebeest muscles were influenced to a greater extent by muscle type than production system or age. Production system had an influence on muscle drip loss; higher values being associated with the semi-extensive system. Age influenced the drip loss, cooking loss, tenderness and lightness of the muscles; the sub-adult meat samples exhibiting the more desirable physical characteristics. Ultimate pH (pHU), drip loss, cooking loss, tenderness and colour were influenced (p ≤ 0.05) by muscle type. The mean pHU values ranged from 5.6 - 5.8, with the forequarter muscles (IS and SS) having a higher pHU (p≤0.05) compared to the other muscles. The drip loss values for the SM muscle (1.9 ± 0.22%) were significantly (p<.0001) higher when compared to the other muscle types. The lowest drip loss values was associated with the IS muscle (1.0 ± 0.07%). Similarly the lowest cooking loss was also associated with IS muscle and the highest for the ST and SM muscles. For tenderness, the highest Warner Bratzler shear force values were observed for the SM muscle (43.6 ± 1.44 N) and the lowest for the forequarter muscles (IS = 24.1 ± 1.16 N and SS = 24.4 ± 1.07 N). All muscles in this study delivered the meat colour associated with game with L* value <40, high a* and low b* values. Production system influenced the moisture, protein and ash content but not the intramuscular fat (IMF) content of the final meat product. Meat from the semi-extensive system had a higher (p ≤ 0.05) protein and ash content, while the extensive system had a higher moisture content (p ≤ 0.05). A significant difference in all the proximate chemical components was observed between the six muscle types. The proximate composition ranging from 75.9 - 78.5% moisture, 19.3 - 22.3% protein, 1.6 - 2.1% IMF and 0.99 - 1.1% ash content. The forequarter muscles were associated with the highest moisture and IMF and lowest protein content. Although production system and muscle type significantly influenced the proximate composition of blue wildebeest meat, the differences were numerically small and therefore it is debatable whether these differences are of biological value and relevance to human nutrition. With the production systems differing in nutritional management, variations in dietary composition and exercise can influence the fatty acid content and consequently the sensory quality of the meat produced. The sensory profile was determine by descriptive sensory analysis (DSA) in addition to various physical measurements (pH, thaw loss, cooking loss and Warner Bratzler shear force) and fatty acid profile to establish the sensory quality of blue wildebeest meat. The main effects had minor influences on the sensory profile with the meat being classified with an intense gamey, beef-like and sweet aroma and flavour. The former being attributed to be due to high concentration of polyunsaturated fatty acids (PUFA). The meat was associated with low tenderness (high shear force) with a relatively moderate initial juiciness and sustained juiciness attributed despite a very low intramuscular fat content of the meat. Differences in fatty acid profiles were attributed more to differences in production systems (differences in diets and activity) than age or anatomical location of muscles. Stearic acid (C18:0), linoleic acid (C18:2n6c) and α-linolenic acid contributed the highest percentage to the total fatty acids, with the meat measuring a PUFA:SFA ratio and n6:n3 (omega 6:omega 3) ratio within the recommended guidelines. With the knowledge that variation in meat quality has been found in animals of the same age and species. An additional eight blue wildebeest bulls (aged 28 months) were obtained from a semi-extensive production system that had a mean undressed carcass weight of 234.1 ± 5.55 kg, a mean carcass weight of 125.4 ± 3.18 kg and a dress out percentage of 53.6 ± 0.56%. The physical meat quality parameters were influenced by muscle type, with the exception of the ultimate pH. The forequarter muscles were found to be desirable with regards to drip loss, cooking loss, Warner Bratzler shear force and intense bright red colour in comparison to the hindquarter muscles. For the chemical analyses it was found that the hindquarter muscles had a lower moisture content, higher protein content and lower intramuscular fat (IMF) content than the forequarter muscles. The optimum aging period for vacuum-packed blue wildebeest LTL and BF muscles was also determined. The muscles were portioned and aged for 2, 5, 9, 14, 20 and 28 days at 4˚C. This study found that to achieve optimum tenderness vacuum packed blue wildebeest LTL muscles should be aged for nine days and BF muscles for fourteen days at 4˚C.

AFRIKAANSE OPSOMMING: Die doel van die studie was om data te verskaf oor die algehele opbrengs en kwaliteit (fisiese eienskappe, chemiese samestelling, sensoriese profiel en optimale verouderingstydperk) van ses spiere [Longissimus thoracis et lumborum (LTL), Biceps femoris (BF), Semimembranosus (SM), Semitendinosus (ST), Infraspinatus (IS) en Supraspinatus (SS)] van blouwildebees bulle (Connochaetes taurinus) geproduseer onder ekstensiewe en semi-ekstensiewe produksiestelsels in Suid-Afrika. Daar is 'n behoefte aan die inligting weens die gebrek aan wetenskaplike inligting oor die vleisgehalte van hierdie spesie en die gevolge van verskeie ekstrinsieke en intrinsieke faktore daarop. In die eerste proef is agt blouwildebees bulle van 'n semi-ekstensiewe produksiestelsel en agt van 'n ekstensiewe produksiestelsel geoes, waar ouderdomme aangepas en verdeel is in volwasse en subvolwasse behandelings. Semi-ekstensiewe blouwildebeeste het getoon dat hulle die potensiaal het om karkasopbrengs te verhoog deurdat hulle beduidende hoër intakte karkas gewigte (208.2 ± 11.14 kg), karkasgewigte (112.1 ± 6.38 kg) en 'n uitslagpersentasie (53.8%) as die ekstensiewe blouwildebeeste (168.8 ± 14.59 kg, 84.9 ± 7.55 kg en 50.2%, onderskeidelik) gehad het. Semi-ekstensiewe blouwildebeeste het ook hoër gewigte vir eksterne en interne afvaldele gehad, asook beduidende (p<.0001) hoër totale spieropbrengste (19.8 ± 0.91 kg) in vergelyking met ekstensiewe diere (14.8 ± 1.22 kg), waar verskille met die lende en agterkwartspiere geassosieer was en nie met die voorkwartspiere nie. Verskille in die fisiese vleiskwaliteitskenmerke van blouwildebees spiere is meer deur spiertipe as produksiestelsel of ouderdom beïnvloed. Produksiestelsel het 'n invloed op die drupverlies van die spier gehad, waar hoër waardes met die semi-ekstensiewe stelsel geassosieer is. Ouderdom het die drupverlies, kookverlies, sagtheid en ligheid van die spiere beïnvloed; die subvolwasse vleismonsters het meer wenslike fisiese eienskappe getoon. Finale pH (pHU), drupverlies, kookverlies, sagtheid en kleur van die vleis is deur spiertipe beïnvloed (p ≤ 0.05). Die gemiddelde pHU waardes het gewissel van 5.6 - 5.8, met die voorkwartspiere (IS en SS) wat 'n hoër (p ≤ 0.05) pHU waarde, in vergelyking met die ander spiere, gehad het. Die drupverlies waardes vir die SM spier (1.9 ± 0.22%) was beduidend (p<.0001) hoër as dié van die ander spiertipes. Die laagste drupverlies waardes is geassosieer met die IS spier (1.0 ± 0.07%). Soortgelyk het die IS spier ook die laagste kookverlies gehad waar die ST en SM spiere weer die hoogste kookverlies gehad het. Vir sagtheid is die hoogste Warner Bratzler skeurkrag waardes vir die SM spier (43.6 ± 1.44 N) en die laagste vir die voorkwartspiere (IS = 24.1 ± 1.16 N en SS = 24.4 ± 1.07 N) waargeneem. Al die spiere het 'n vleiskleur gehad wat tipies met wildsvleis geassosieer word (d.i. L* waardes <40, hoë a* waardes en lae b* waardes). Produksiestelsel het die vog-, proteïen-, en asinhoud beïnvloed, maar nie die intramuskulêre vetinhoud (IMF) van die finale vleisproduk nie. Vleis van die semi-ekstensiewe stelsel het 'n hoër (p ≤ 0.05) proteïen- en asinhoud gehad, terwyl vleis van die ekstensiewe stelsel 'n hoër voginhoud (p< 0.05) gehad het. 'n Beduidende verskil is waargeneem vir al die proksimale chemiese komponente tussen die ses spiertipes. Die proksimale samestelling het gewissel van 75.9 - 78.5% vog-, 19.3 - 22.3% protein-, 1.6 - 2.1% IMF- en 0.99 - 1.1% asinhoud. Die voorkwartspiere word met die hoogste voginhoud en IMF-inhoud en die laagste proteïeninhoud geassosieer. Alhoewel produksiestelsel en spiertipe die proksimale samestelling van blouwildebeesvleis beduidend beïnvloed het, was die verskille numeries klein en daarom is dit debatteerbaar of hierdie verskille biologiese waarde of relevansie vir menslike voeding het. Met die produksiestelsels wat verskil in voedingsbestuur, kan variasies in diëtsamestelling en oefening die vetsuurinhoud en gevolglik die sensoriese kwaliteit van die vleis wat geproduseer word, beïnvloed. Die sensoriese profiel is met beskrywende sensoriese analise (descriptive sensory analysis, DSA) bepaal, bykomend tot verskeie fisiese metings (pH, ontdooiverlies, kookverlies en Warner Bratzler skeurkrag) en vetsuur profilering om die sensoriese gehalte van blouwildebees vleis te bepaal. Die hoof effekte het klein invloede op die sensoriese profiel gehad, met die vleis wat met 'n intense wild, beesagtige en soet aroma en geur geklassifiseer is. Eersgenoemde word toegeskryf aan 'n hoë konsentrasie poli-onversadigde vetsure (polyunsaturated fatty acids, PUFA). Die vleis was geassosieer met 'n lae sagtheid (hoë skeurkrag) met 'n relatiewe gematigde aanvanklike sappigheid en volgehoue sappigheid toegeskryf ondanks die vleis se lae IMF-inhoud. Verskille in vetsuur profiele is meer toegeskryf aan verskille in produksiestelsels (d.i. verskille in diëte en aktiwiteit) as die verskille in ouderdom of anatomiese ligging van spiere. Steariensuur (C18:0), linoleïensuur (C18:2n6c) en α-linoleïesuur het die hoogste persentasie tot die totale vetsuur samestelling bygedra. Die vleis het ook PUFA:SFA (polyunsaturated fatty acids:saturated fatty acids) en n6:n3 (omega 6:omega 3) vetsuur verhoudings binne die aanbevole riglyne bevat. Met die wete dat variasie in vleiskwaliteit gevind is in diere van dieselfde ouderdom en spesies, is agt bykomende blouwildebees bulle (28 maande oud) met 'n gemiddelde intakte karkasgewig van 234.1 ± 5.55 kg, 'n gemiddelde karkasgewig van 125.4 ± 3.18 kg en 'n uitslagpersentasie van 53.6 ± 0.56%, verkry uit 'n semi-ekstensiewe produksiestelsel. Die fisiese vleiskwaliteit parameters is beïnvloed deur spiertipe, met die uitsondering van die pHU. Die voorkwartspiere was wenslik met betrekking tot drupverlies, kookverlies, Warner Bratzler skeurkrag en intense helder rooi kleur in vergelyking met die agterkwartspiere. Volgens die chemiese analises, het die agterkwartspiere 'n laer voginhoud, hoër proteïeninhoud en laer IMF-inhoud as die voorkwartspiere gehad. Die optimale verouderingstydperk vir vakuum verpakte blouwildebees LTL en BF spiere is ook vasgestel. Die spiere is in porsies verdeel en verouder vir 2, 5, 9, 14, 20 en 28 dae by 4°C. Daar is bevind dat optimale sagtheid bereik word wanneer die vakuum verpakte blouwildebees LTL spiere vir nege dae en BF spiere vir veertien dae by 4°C verouder word.

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