Interventions to enhance the quality of South African chevon

Thesis (PhDAgric)--Stellenbosch University, 2021.

ENGLISH ABSTRACT: Goat meat is not readily available commercially in South Africa, probable as preferences of the post-Apartheid new upcoming middle-class consumer is not yet taken into consideration. Historically, little is known about goat meat characteristics and perceptions exist that “indigenous” goats produce tougher meat than Boer Goats (BG), synthetically bred to be a meat producing breed making use of the original pure-bred large frame Indigenous Veld Goats (IVG) such as the Cape Lob Ear. With time, uncontrolled cross-breeding between BG with small frame “indigenous” goats increased and these small mostly monotonous white or white and brown goats, labelled “indigenous” and then perceived as too small and not suitable for meat production. Fortunately, some farmers conserved the original large frame IVG eco-types of Southern Africa and saved them from extinction. The aim of the study was to investigate interventions (castration and electrical stimulation) on carcass-, muscle- and meat characteristics of same-aged young wethers and bucks of BG and IVG (Cape Speckled and the Cape Lob Ear), to determine whether IVG could have a similar potential for quality meat production under the same production conditions. Goat muscles are small and forced the project to be performed in two phases to enable all envisaged analyses. The first phase described factors influencing tenderness, and colour attributes of six muscles. The second phase evaluated carcass characteristics, meat tenderness, the calpain system related to ageing, pre-rigor muscle energy profile, meat colour, the volatile profile, and resultant sensory characteristics. Outcomes were that wethers, compared to bucks had higher dressing %, subcutaneous fat % in all primal cuts, intramuscular fat (IMF) %, kidney fat % and, overall, slightly less bone %. Variations in meat characteristics such as pH, temperature, water holding capacity, % drip loss, myofibril fragment length, IMF, connective tissue characteristics, and Warner-Bratzler shear force (WBSF) between the muscles were found. The Longissimus thoracis et lumborum (LTL) had the highest shear force values (>40.0 N), followed by Biceps femoris (BF), Semitendinosus (ST), Semimembranosus (SM), Supraspinatus (SS), and Infraspinatus (IS). Bucks were less tender (P ≤ 0.05) compared to wethers; calpastatin (higher values for bucks) could explain these sex-related differences for WBSF. Calpain-2 played a greater role in tenderisation suggesting that the activation of the system occurred at a later stage than in other species. The pHu values >5.6 were linked with meat being darker (L* <31), having lower 24 hours post-mortem muscle glycogen (18 μmol/g) and lactate levels (25 μmol/mg). High initial lactate concentration, >35 μmol/g (LTL muscle) and low glycolytic potential (GP) (<94 μmol/g), suggested that goats suffered from both chronic and acute stress during ante-mortem handling. Overall, the scores for the various sensory attributes were low (<4.00 on a 1 to 8 scale), apart from goat aroma and goat-like flavour (>4.00). A total of fifteen volatile compounds were identified and quantified in the LTL and SM. The present study showed that it is important to use the correct pre- and post-slaughter conditions to process goats as incorrect procedures could give way to negative perceptions on this commodity.

AFRIKAANSE OPSOMMING: Bokvleis is nie kommersieёl geredelik beskikbaar in Suid-Afrika nie, waarskynlik omdat die post- Apartheid opkomende middelklasverbruiker nog nie in ag geneem word nie. Histories is daar min bekend oor bokvleiskenmerke en persepsies bestaan dat bokke oor die algemeen taaier vleis met onaangename reuke produseer. Nietemin is Boerbokke (BG) gedurende die 1900’s sinteties geteel om 'n vleisproduserende ras te wees deur onderandere gebruik te maak van die oorspronklike groot raam Inheemse Veldbokke (IVG) en meer spesifiek die Kaapse Hang Oor. Met verloop van tyd het ongekontroleerde kruisteling tussen BG met kleinraam “inheemse” bokke toegeneem. Hierdie meestal wit- of wit- en bruin kleurige bokke, het verkeerdelik begin bekend staan as “inheemse” bokke en is beskou as minderwaardig vir vleisproduksie. Gelukkig het sommige boere die oorspronklike grootraam IVG eko-soorte van Suid-Afrika bewaar en hulle van uitwissing gered. Die doel van die studie was om intervensies te ondersoek (kastrasie en elektriese stimulering) op karkas- en vleiseienskappe van jong gekastreerde- en intakte ramme van dieselfde ouderdom van BG en IVG (Kaapse Spikkel en die Kaapse Hang Oor) om te bepaal of IVG onder dieselfde produksietoestande 'n soortgelyke potensiaal vir vleisproduksie van gehalte kan hê. Bokspiere is klein en dwing die projek om in twee fases uitgevoer te word om alle beoogde ontledings moontlik te maak. In die eerste fase word faktore beskryf wat die sagtheid en kleurkenmerke van ses spiere beïnvloed. Die tweede fase het die karkaskeienskappe, die sagtheid van die vleis, die kalpainstelsel wat verband hou met veroudering, voor-rigor spierenergieprofiel, vleiskleur, die vlugtige vetsuur profiel en die gevolglike sensoriese eienskappe beoordeel. Die resultate toon dat kastrate in vergelyking met die intakte ramme, hoër uitslag %, onderhuidse vet % in alle primêre snitte, binnespierse vet (IMF) %, niervet % en, in die algeheel effens laer been % gehad het. Variasies in vleiskenmerke soos pH, temperatuur, waterhouvermoë, % drupverlies, myofibril-fragmentasie- lengte, IMF, bindweefselkenmerke en Warner-Bratzler-skeurkrag (WBSF) tussen die spiere is gevind. Die Longissimus thoracis et lumborum (LTL) het die hoogste skeurkragwaardes (>40.0 N) gehad, gevolg deur Biceps femoris (BF), Semitendinosus (ST), Semimembranosus (SM), Supraspinatus (SS) en Infraspinatus (IS). Intakte ramme was taaier (P ≤ 0.05) in vergelyking met kastrate; kalpastatien (hoër waardes vir intakte ramme) kon hierdie geslagsverwante verskille vir WBSF verklaar. Kalpaïen-2 het 'n groter rol gespeel in die versagtings proses, wat daarop dui dat die aktivering van die stelsel op 'n later stadium plaasgevind het as in ander spesies. Die pHu- waardes >5.6 was gekoppel daaraan dat vleis donkerder was (L* <31), met 'n laer 24 uur spierglikogeen (18 µmol/g) en laktaatvlakke (25 µmol/mg). Hoë aanvanklike laktaatkonsentrasie, >35 µmol/g (LTL-spier) en lae glykolitiese potensiaal (GP) (<94 µmol/g), het voorgestel dat bokke tydens kroniese en akute spanning aan kroniese en akute spanning kon gely het. In die algeheel was die waardes vir die verskillende sensoriese eienskappe laag (<4.00 op 'n skaal van 1 tot 8), afgesien van bok-aroma en bok-smaak (>4.00). Altesaam vyftien vlugtige vetsure is geïdentifiseer en gekwantifiseer in die LTL en SM. Die huidige studie het getoon dat dit belangrik is om die regte voor- en na-slag prosedures te gebruik om bokke te prosesseer, aangesien verkeerde prosedures negatiewe persepsies oor hierdie kommoditeit kan ondersteun.

Doctoral