Meat quality characteristics of giraffe (Giraffa camelopardalis angolensis)

Silberbauer, Bianca Louise (2020-03)

Thesis (MScAgric)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Although some giraffe populations are threatened, their numbers have been seen to grow exponentially under ranched management conditions. This population growth can be attributed to the absence of natural predators and therefore periodic culling is essential to control their population numbers and thus prevent them from exceeding carrying capacity. These culls result in a large quantity of meat, of which very little is known of the quality. This study aimed to quantify the effect of sex on the yields of fresh cuts from giraffe, and the meat quality thereof as well as the yields and chemical composition of the red offal. For this study sixteen giraffe (Giraffa camelopardalis angolensis) (eight male; eight female) were culled, the majority were relatively young (2½ – 6 years old), however, one female was found to be mature (± 9 years), her data was therefore removed from all analyses except the sensory analysis, to avoid the effect of age. Various body measurements and commercial carcass yields were investigated to quantify the effect of sex there upon. The dead weight and carcass weight was not significantly affected by the sex, however, the males did tend to be heavier (dead weight: males = 691.1 ± 45.47 kg; females = 636.5 ± 33.76 kg; P = 0.096; carcass weight: males = 393.1 ± 28.52 kg; females = 359.5 ± 14.49; P = 0.053). The giraffe were found to have a favourable dressing percentage of ~57 % for both sexes. The foreleg measurements and horn measurements were all larger for the males than the females (P <0.05), despite the relatively young age. The moisture % of the red offal (heart, liver, kidneys and tongue) averaged ~76 %, the protein % averaged ~17 %, the total fat % averaged ~5 % and the ash % averaged ~1 % across both sexes of the giraffe. The red offal had a favourably high protein content as well as a low fat content, which when combined with the high yields thereof per animal, indicates that giraffe offal can serve as a source of low cost protein. The meat yields were investigated, and eight muscles (Longissimus thoracis et lumborum muscle (LTL), Semimembranosus muscle (SM), Biceps femoris muscle (BF), Semitendinosus muscle (ST), Gluteus medius muscle (GM), Supraspinatus muscle (SS), Infraspinatus muscle (IS), and Psoas major muscle (PM)) were removed from each giraffe and the physical meat quality thereof was assessed. The Warner-Bratzler shear force (WBSF) was affected by a significant interaction between sex and muscle (P <0.001), the interaction for the CIE L* values also tended towards significance (P = 0.054). The cooking loss (male = 41.6 ± 0.35 %; female = 40.7 ± 0.33 %; P = 0.024) was found to be higher in males. Muscle had a significant effect on all physical parameters. The ultimate pH of all muscles was in the acceptable range (5.5 – 5.9); the WBSF of all the samples was found to be <43 N which is classified as tender. The meat colour was lighter than most game meat; the myoglobin content of the muscles was found to range from 5.1-9.3 mg/g with a significant interaction between sex and muscle (P = 0.001) with higher myoglobin levels resulting in lower L* values and hue-angles. The chemical composition of the eight muscles was assessed in terms of moisture (77.2 ± 0.09 g/100 g), protein (20.8 ± 0.09 g/100 g), intramuscular fat (IMF) (1.4 ± 0.03 g/100 g) and ash (1.1 ± 0.01 g/100 g). There was a significant interaction between sex and muscle for the moisture (P = 0.044), protein (P = 0.045) and ash (P = 0.042) contents, while muscle (P <0.001) had an effect on the fat content. The mineral content of the bone, liver and LTL muscle was also analysed, the bone was found to have a calcium to phosphorus ratio of 2:1 despite a diet low in phosphorus. The liver and LTL were both high in iron and other essential micro- and macro-minerals. The sensory profile of the LTL muscle of the giraffe as affected by sex was assessed on a 100-point line scale. It was found that the instrumental tenderness of the giraffe meat was considered tough (WBSF >53 N), however, this did not have a strong correlation (r = - 0.616; P = 0.011) with sensory tenderness (~52). The effect of sex was limited, but the males were found to have a higher gamey and metallic aroma, while the females had a higher liver-like flavour than males. The panellists reported to find high intensities of the metallic (~23), sour- (~14) and sweet- (~25) associated and black pepper (~9) attributes of the giraffe meat in this study. The fatty acid profile of the LTL muscles was also analysed and it was found that both sexes had a low intramuscular fat (IMF) content (1.4 - 1.7 %). The polyunsaturated fatty acid to saturated fatty acid (PUFA:SFA) ratios and the n-6:n-3 PUFA ratios as well as the Atherogenicity index were favourable for inclusion in a healthy diet. This study also investigated the effect of post-mortem aging on the tenderness and other physical parameters of the LTL, SM and BF steaks from male and female giraffe in order to determine the ideal ageing period. The tenderness improved until day 22 (19.1 ± 0.30 N) of the 38 day ageing period, after which it plateaued. The colour improved, in terms of redness and saturation, until day 18 (L* = 44.1 ± 0.29; chroma = 22.0 ± 0.15), thereafter discolouration occurred. There was progressive purge loss throughout the ageing period. Therefore, it is recommended to vacuum-age giraffe meat for no more than 18 days.

AFRIKAANSE OPSOMMING: Alhoewel sommige kameelperd populasies bedreig word, kan hulle getalle eksponensieel groei onder boerdery bestuuromstandighede. Hierdie populasie groei kan toegeskryf word aan die afwesigheid van natuurlike roofvyande en dus is periodieke uitdunning noodsaaklik om hulle bevolkingsgetalle te beheer en sodoende te voorkom dat hulle die drakrag oorskry. Hierdie oespraktyke lei tot die oplewering van groot hoeveelheid vleis met steeds onbekende kwaliteit eienskappe. Die doel van die studie was om die effek van geslag op die opbrengste van vars snitte en die vleiskwaliteit daarvan te kwantifiseer, asook om die opbrengste en chemiese samestelling van die rooi afval van kameelperd te bepaal. Vir hierdie studie is sestien kameelperde (Giraffa camelopardalis angolensis) (agt manlik; agt vroulik) geoes, die meerderheid van hierdie diere was relatief jonk (2½ - 6 jaar oud), maar daar was egter een vroulike volwasse dier wat as ʼn uitskieter hanteer was (± 9 jaar). Hierdie individu se data was dus uit alle ontledings verwyder, behalwe die sensoriese analise om die effek van ouderdom te ontwyk. Verskeie liggaamsmetings en kommersiële karkasopbrengste was ondersoek om die effek van geslag daarop te kwantifiseer. Daar was nie noemenswaardige verskille tussen die dooiegewig en karkasgewig van manlike en vroulike diere gevind nie, die manlike diere was egter geneig om swaarder te wees (dooie gewig: mans = 691.1 ± 45.47 kg; vroulike diere = 636.5 ± 33.76 kg; P = 0.096; karkasgewig: mans = 393.1 ± 28.52 kg; wyfies = 359.5 ± 14.49; P = 0.053). Beide manlike en vroulike kameelperde het gunstige uitslagpersentasies getoon (~57 %). Die manlike diere het langer voorbeenmetings en horingmetings as die vroulike diere (P <0.05) getoon ongeag die relatiewe jong ouderdom. Die gemiddelde vog, proteïen, totale vet en as persentasie van die rooi afval (hart, lewer, niere en tong) was ~76 %, ~17 %, ~5 %, ~1 %, onderskeidelik vir beide geslagte van die kameelperd. Die rooi afval het 'n gunstige hoë proteïeninhoud sowel as 'n lae vetinhoud gehad wat tesame met die hoë opbrengste per dier daarop dui dat kameelperdafval kan dien as ʼn bekostigbare proteïene bron. Agt spiere (Longissimus thoracis et lumborum muscle (LTL), Semimembranosus muscle (SM), Biceps femoris muscle (BF), Semitendinosus muscle (ST), Gluteus medius muscle (GM), Supraspinatus muscle (SS), Infraspinatus muscle (IS), and Psoas major muscle (PM)) van elke dier was verwyder, waarvan die opbrengste en fisiese vleiskwaliteit bepaal is. Die Warner-Bratzler skeurkrag (WBSF) was beïnvloed deur 'n beduidende interaksie tussen geslag en spier (P <0.001), die interaksie van die CIE L* waardes was ook geneig om betekenisvol te wees (P = 0.054). Die kookverlies van manlike diere (manlik = 41.6 ± 0.35 %; vroulik = 40.7 ± 0.33 %; P = 0.024) was hoër as die van die vroulike diere. Spiere het 'n beduidende effek op alle fisiese eienskappe gehad. Die uiteindelike pH van al die spiere was in normale grense (5.5 – 5.9); daar is gevind dat die WBSF van alle toetssnitte <43 N was, en kan as sag geklassifiseer word. Die vleiskleur van die spiere was egter ligter as die van meeste wildsspesies. Daar was ook gevind dat die mioglobieninhoud van die spiere tussen 5.1 en 9.3 mg/g gewissel het met 'n beduidende interaksie tussen geslag en spier (P = 0.001) met hoër mioglobienvlakke, wat gelei het tot laer L * waardes en kleurtoon. Die chemiese samestelling van die agt spiere was bepaal deur die vog- (77.2 ± 0.09 g/100 g), proteïen- (20.8 ± 0.09 g/100 g), intramuskulêre vet- (IMF) (1.4 ± 0.03 g/100 g) en asinhoud (1.1 ± 0.01 g/100 g) te kwantifiseer. Daar was 'n beduidende interaksie tussen geslag en spier vir die vog- (P = 0.044), proteïen- (P = 0.045) en asinhoud (P = 0.042), die spier (P <0.001) 'n effek op die vetinhoud gehad het. Die mineraalinhoud van die been, lewer en LTL was ook ontleed, en daar is gevind dat die been 'n 2:1 verhouding van kalsium tot fosfor gehad het, ongeag 'n dieet met 'n lae fosforinhoud. Die lewer en LTL was albei hoog in yster en ander essensiële mikro- en makrominerale. Die sensoriese profiel van die kameelperd se LTL spier, wat deur geslag beïnvloed was, was op 'n 100 punt lynskaal geassesseer. Daar is gevind dat die instrumentele sagtheid van die kameelperdvleis as taai beskou kan word (WBSF >53 N), maar dit het nie 'n sterk korrelasie (r = - 0.616; P = 0.011) met die sensoriese sagtheid gehad nie (~52). Die effek van geslag was nie prominent nie, maar daar is gevind dat die manlike diere 'n hoër wild- en metaalagtige aroma getoon het, terwyl die vroulike diere 'n hoër leweragtige smaak gehad het as die manlike diere. Volgens die paneellede was daar hoë intensiteit van metaal- (~23), suur- (~14), soet- (~25) en swartpeper (~9) kenmerke van die kameelperdvleis in hierdie studie. Die vetsuurprofiel van die LTL spier is ook ontleed en daar is gevind dat beide geslagte 'n lae inhoud van intramuskulêre vet (IMF) (1.4 – 1.7 %) gehad het. Die verhoudings van poli-onversadigde vetsure tot versadigde vetsure (PUFA: SFA) en die n-6: n-3 PUFA-verhoudings, sowel as die Atherogene (Atherogenicity) indeks was gunstig vir die insluiting in 'n gesonde dieet. Hierdie studie het ook die effek van post-mortem veroudering op die sagtheid en ander fisiese eienskappe van die LTL, SM en BF toetssnitte van manlike en vroulike kameelperde ondersoek om die ideale verouderingstydperk te bepaal. Die sagtheid het verbeter tot dag 22 (19.1 ± 0.30 N) van die 38 dae verouderingsperiode, waarna dit afgeplat het. Die kleur het, ten opsigte van rooiheid en kleur intensiteit verbeter tot op dag 18 (L * = 44.1 ± 0.29; chroma = 22.0 ± 0.15), daarna het verkleuring plaasgevind. Daar was progressiewe vogverlies gedurende die verouderingsperiode. Daarom word dit aanbeveel dat kameelperdvleis nie langer as 18 dae onder vakuum toestande verouder moet word nie.

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