The meat quality of bontebok (Damaliscus pygargus pygargus)

Jordaan, Kayla-Anne (2020-03)

Thesis (MScAgric)--Stellenbosch University, 2020.


ENGLISH ABSTRACT: The aim of this study was to establish baseline data for the South African meat industry on the meat quality of bontebok (Damaliscus pygargus pygargus) males and to investigate the influence of muscles (Longissimus thoracis et lumborum/LTL, semimembranosus/SM, biceps femoris/BF, infraspinatus/IS, semitendinosus/ST, supraspinatus/SS and the psoas major/fillet) on the meat quality of the former species. Carcass yields, overall meat quality (physical characteristics and chemical composition), optimum ageing period, microbial activity/safety and sensory attributes of bontebok meat were established and compared to its closely related sub-species, the blesbok (Damaliscus pygargus phillipsi), where applicable. Two trials were conducted: one in March (n=12) and one in April (n=8). All seven above-mentioned muscles were quantified for carcass composition (April and March trial) and chemical characteristics (March trial), however, physical characteristics were determined for all seven muscles in the March trial but only for three muscles in the April trial (SM, BF and LTL). Ageing and microbial tests was performed on the LTL muscle from the April bontebok. Sensory attributes were compared using two muscles (BF and SM) from bontebok (n=7) and blesbok (n=7), both species harvested in April. The carcass yields of bontebok was similar to that of blesbok as established in literature. The dressing percentages (calculated from warm carcass weight) of bontebok were 50.4% (± 1.55) and 50.7% (± 3.07) for March and April, respectively. Furthermore, the muscle with the largest percentage of the cold carcass weight, was the LTL muscle in both March (3.1 ± 0.05%) and April (2.8 ± 0.22%), whereas the fillet was the smallest muscle, contributing least towards the cold carcass weight, in both March (0.4 ± 0.03%) and April (0.4 ± 0.04%). Additionally, the external offal (head, horns, skin and genitals) percentages were higher in March (14.4 ± 0.88%) and April (15.1 ± 0.77%) than internal offal percentages (stomach, organs and intestines) in March (34.4 ± 0.96%) and April (31.7 ± 3.49%). All physical and chemical characteristics were influenced (p ≤ 0.05) by muscles in the March trial and only ultimate pH (pHu) and cooking loss percentage in the April trial (p ≤ 0.05). The pHu values found for bontebok harvested in March were high (5.84-6.21) and drip loss percentages were generally low (0.7%-0.9%). The fillet and forequarter muscles (IS and SS) had the highest pHu values (>6.1) and the lowest Warner-Bratzler shear force values (more tender). The IS muscle had the lowest cooking loss percentage of 28.9% (± 2.57) (p ≤ 0.05). Furthermore, the muscles that were most red were the forequarter muscles and fillet (a* = 12.96-13.73) and the lightest muscle was the ST (L* = 35.90). From the three muscles analysed (SM, BF and LTL) in the April trial, the average pHu values were lower than found for March bontebok with the BF muscle having a significantly higher pHu (5.71) than the LTL muscle (5.50). The cooking loss percentage in the latter trial was found to be significantly higher in the SM muscle (38.8 ± 1.09%) than the BF (35.3 ± 1.48%) and LTL (34.7 ± 2.87%) muscles. The chemical composition of bontebok meat resulted in meat with extremely low average intramuscular fat (IMF) contents (0.8 g/100 g) with the fillet containing the highest IMF content (1.1 g/100 g). The two hindquarter (BF, SM) muscles and the LTL muscle had significantly higher protein (~23.0 g/100 g meat) and lower moisture (~75.5 g/100 g meat) contents than the other muscles analysed. The ash content was significantly lower in the forequarter muscles: IS (1.1 g/100 g meat); and SS (1.16 g/100 g meat) than the other muscles analysed. Although the differences between muscles were significant, they are also marginal and thus may not be of biological value in terms of human nutrition. Regardless, all bontebok meat had low IMF and high protein contents which could be preferred by modern-day consumers that regard a low-fat and high protein diet as “healthy”. The LTL muscle of eight male bontebok was aged over eight separate time points (day 1, 2, 4, 6, 7, 8, 10, and 12). Bontebok meat tenderised rapidly and the optimum ageing time for bontebok LTL steaks was determined to be eight days at 4°C under vacuum packaging conditions. The Warner-Bratzler shear force (WBSF) decreased until an optimum tenderness for this ageing trial was reached on day 8 (57.2 N) after which it plateaued until day 12. The decrease in tenderness was associated with an improved meat colour and increase in cumulative purge loss over time. Furthermore, the microbial activity over time indicated that no significant effects were detected for total plate count (TPC) or Escherichia coli/coliforms between ageing time points and all counts (log CFU/g) were within specified safety limits. Additionally, all bontebok samples tested negative for the presence of Salmonella. With the similarity in diets for bontebok and blesbok (both strict grazers), differences in terms of sensory attributes between the latter species were expected to be minor during a descriptive sensory analysis (DSA) where two muscles (SM and BF) of blesbok and bontebok were compared. No differences were found in flavour or aroma profiles between species or muscle type (p ≥ 0.05), except gamey flavour that was slightly higher in blesbok than bontebok. Gamey flavour (~75) and aroma (~74) proved to be the largest contributors to overall flavour and aroma on a 100-point scale (0=none; 100= prominent). Certain textural attributes differed significantly between species and muscle type. The bontebok had a significantly higher WBSF, lower sensory tenderness, higher residue and lower mealiness compared to blesbok and the SM muscle proved to be superior compared to the BF muscle due to its significantly higher sensory tenderness and initial juiciness. Regardless, bontebok meat compares favourably to blesbok meat and it is postulated that meat consumers would struggle to differentiate between blesbok and bontebok meat. Overall, bontebok meat proved to be safe and of good quality and could be utilised in the South African game meat industry. The meat was significantly influenced by muscle type and compared well to its closely related sub-species, the blesbok.

AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om basisdata vir die Suid-Afrikaanse vleisbedryf op die vleiskwaliteit van bontebok (Damaliscus pygargus pygargus) ramme vas te stel en om die invloed van spiere te ondersoek (Longissimus thoracis et lumborum/LTL, semimembranosus/SM, biceps femoris/BF, infraspinatus/IS, semitendinosus/ST , supraspinatus/SS en die psoas major/filet) op die vleiskwaliteit van die voormalige spesie. Karkasopbrengs, algehele vleiskwaliteit (fisiese eienskappe en chemiese samestelling), optimale verouderingstydperk, mikrobiese aktiwiteit /veiligheid en sensoriese eienskappe van bontebok vleis was bepaal en vergelyk met sy nouverwante sub-spesie, die blesbok (Damaliscus pygargus Phillipsi), waar van toepassing. Twee proewe is uitgevoer: een in Maart (n = 12) en een in April (n = 8). Al sewe bogenoemde spiere is gekwantifiseer vir karkas samestelling (April en Maart proef), chemiese eienskappe (Maart proef) en fisiese eienskappe in die Maart proef, maar net vir drie spiere in die April proef (SM , BF en LTL). Veroudering en mikrobiese toetse is uitgevoer op die drie spiere van die April bontebok. Sensoriese eienskappe is vergelyk tussen twee spiere (BF en SM) van bontebok (n = 7) en blesbok (n = 7) spesies, albei in April geoes. Die karkasopbrengs van bontebok was soortgelyk aan die van blesbok soos in literatuur vasgestel. Die afslagpersentasies (bereken vanaf warm karkasgewig) van bontebok was 50.4 % (± 1.55) en 50.7% (± 3.07) vir Maart en April proewe, onderskeidelik . Die spier met die grootste persentasie van die koue karkasgewig was die LTL-spier in beide Maart (3.1 ± 0.05%) en April (2.8 ± 0.22%), terwyl die filet die kleinste spier was en die minste bygedra het tot die koue karkas gewig, in beide Maart (0.4 ± 0.03%) en April (0.4 ± 0.04%). Boonop was die eksterne afval (kop, horings, vel en geslagsdele) persentasies hoër in Maart (14.4 ± 0.88%) en April (15.1 ± 0.77%) as interne afvalpersentasies (maag, organe en ingewande) in Maart (34.4 ± 0.96%) en April (31.7 ± 3.49%). Al die fisiese en chemiese eienskappe is beïnvloed (p ≤ 0.05) deur die spiere in die Maart proef en slegs die uiteindelike pH (pHu) en die kookverliespersentasie in die April proef (p ≤ 0.05). Die pHu waardes vir die Maart bontebok was hoog (5.84-6.21) en die persentasie drupverlies was oor die algemeen laag (0.7%-0.9%). Die filet- en voorlyfspiere (IS en SS) het die hoogste pHu waardes (>6.1) en die laagste Warner-Bratzler skuifkragwaardes (meer sag). Die IS-spier het die laagste kookverlies persentasie gehad (28.9 ± 2.57%) (p ≤ 0.05). Verder was die rooiste spiere die voorlyfspiere en filet (a *= 12.96-13.73) en die ligste spier was die ST (L *=35.90). Van die drie spiere wat geanaliseer is (SM, BF en LTL) in die April-proef, was die gemiddelde pHu waardes laer as gevind vir Maart bontebok, met die BF-spier met 'n hoër beduidende pHu (5,71) as die LTL-spier (5.50). Die persentasie kookverlies in laasgenoemde proef was aansienlik hoër in die SM-spier (38.8 ± 1.09%) as die BF (35.3 ± 1.48%) en LTL (34.7 ± 2.87%) spiere. Die chemiese samestelling van bontebokvleis het gelei tot vleis met 'n buitengewoon lae binnespier vet inhoud (0.8 g/100 g), met die filet wat die hoogste vet inhoud gehad het (1.1 g/100 g). Die twee agterkwart (BF, SM) spiere en die LTL spier het ‘n aansienlike hoër proteïen (~23.0 g/100 g vleis) en 'n laer vog inhoud (~75,5 g/100 g vleis) gehad as die ander spiere wat geanaliseer is. Die as-inhoud was aansienlik laer in die voorlyfspiere: IS (1.1 g/100 g vleis); en SS (1.16 g/100 g vleis) as die ander spiere wat ontleed is. Alhoewel die verskille tussen spiere beduidend was, is hulle moontlik nie van biologiese waarde in terme van menslike voeding nie. Alle bontebokvleis het 'n lae vet en hoë proteïen inhoud gehad. Moderne verbruikers wat 'n lae-vet/hoë proteïen dieët as 'gesond' beskou, sal die bontebok vleis verkies bo ander kommersiële rooivleis. Die LTL-spier van agt manlike bontebokke is verouder vir agt afsonderlike tydpunte (dag 1, 2, 4, 6, 7, 8, 10 en 12). Bontebok vleis het vinnig versag oor tyd en die optimale verouderings tydperk vir bontebok LTL steaks was bepaal as agt dae by 4°C onder vakuum verpakking. Die Warner-Bratzler- skuifkrag (WBSK) het afgeneem totdat 'n optimale sagtheid vir hierdie verouderingsproef op dag 8 (57.2 N) bereik is, waarna dit ‘n plato bereik het tot dag 12. Die afname in sagtheid het gepaard gegaan met 'n verbetering in vleiskleur en ’n toename in kumulatiewe vog verlies met verloop van tyd, met aanvaarbare gewigsverliespersentasies tot op dag 10, waarna die gewigsverlies >4% was, wat gekenmerk is as onaanvaarbaar deur algemene verbruikers. Verder het die mikrobiese aktiwiteit met verloop van tyd geen noemenswaardige effekte waargeneem vir totale plaattelling (TPC) of Escherichia coli/coliforms tussen verouderingstydpunte nie. Verder, het alle mikrobiese tellings (log CFU/g) binne spesifieke veiligheidsgrense geval. Alle bontebok vleis monsters het ook negatief getoets vir die teenwoordigheid van Salmonella. Daar is ‘n streng ooreenkoms tussen diëte van bontebok en blesbok (albei streng grasvreters), daarom sou die verskille ten opsigte van sensoriese eienskappe tussen laasgenoemde spesies na verwagting klein wees. Tydens 'n beskrywende sensoriese analise (BSA), waar twee spiere (SM en BF) van blesbok en bontebok vergelyk is, was daar geen verskille in aroma- of smaakprofiele tussen spesies of spiersoort (p ≥ 0.05) gevind nie, behalwe ‘n wildsagtige geur wat effens hoër in blesbok as bontebok was. Wildagtige geur- (~75) en aroma (~74) was die grootste bydraer tot die algehele geur en aroma op 'n 100-punt skaal (0=geen; 100=prominent) . Sekere tekstuurkenmerke het betekenisvol tussen spesies en spiersoort verskil. Die bontebok het 'n aansienlike hoër WBSK, 'n laer sensoriese sagtheid, 'n hoër residu en laer “mealiness” in vergelyking met blesbok gehad. Die SM-spier blyk beter te wees in vergelyking met die BF-spier vanweë die aansienlike hoër sensoriese sagtheid en aanvanklike sappigheid. Hoe dit ook al sy, bontebokvleis vergelyk goed met blesbokvleis en dit word gestel dat vleisverbruikers sou sukkel om tussen blesbok- en bontebokvleis te onderskei. In die algemeen is bontebokvleis veilig om te eet en van goeie gehalte en kan in die Suid-Afrikaanse wildsvleisbedryf gebruik word. Die vleis is aansienlik beïnvloed deur spiersoort en vergelyk goed met sy nou verwante subspesie, die blesbok.

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