Physichemical and microbiological attributes of black wildebeest (Connechaetes gnou) muscles

Ndyoki, Fundeka Patience (2018-03)

Thesis (MScFoodSc)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: The study characterised the physicochemical and microbiological-related meat quality attributes of six muscles [Longissimus thoracis et lumborum (LTL), Biceps femoris (BF), Infraspinatus (IS), Supraspinatus (SS), Semimembranosus (SM) and Semitendinosus (ST)] harvested from culled mature male and female black wildebeest (Connochaetes gnou). Descriptive information regarding the respective muscles included carcass characteristics, physical attributes (pH, surface colour, drip loss percentage, weep loss percentage, cooking loss percentage and Warner-Bratzler shear force), chemical attributes (moisture, protein, fat, ash, lipid oxidation and fatty acids profile) and microbiological attributes (total viable count and Enterobacteriaceae). Sex and harvesting year were considered as main effects when analysing carcass characteristics, while sex and muscle type were the main effects regarding determination of the physicochemical quality attributes of all muscles. Muscle type and ageing time were the main effects considered in determining the influence of ageing of the LTL and BF muscles. The average live weight of animals harvested in 2016, did not differ from that harvested in 2017 (149.5 ± 4.23 kg vs. 163.4 ± 5.92kg). Male black wildebeest had a heavier live weight (141.4 ± 5.92kg), and heavier warm and cold carcass weight (89.8 ± 1.91 kg and 85.8 ± 1.99 kg), when compared to the live weight (117.4 ± 4.23kg) and warm and cold carcass weight (71.0 ± 2.67kg and 68.6 ± 2.79 kg) recorded for female animals. The dressing percentage for male black wildebeest (50.2 ± 0.62%) did not differ from that of female animals (48.6 ± 0.87%). Weights of the trachea and lungs were heavier in the animals harvested in 2017. Heavier hide, head, tongue, trotters, heart and spleen weights were recorded for male black wildebeest. Consumable offal (excluding the gastrointestinal tract) contributed 12.7% to male live weights, and 11.2% to female live weight, respectively. A significant sex effect was observed on the % composition of total polyunsaturated fatty acids (PUFA), total saturated fatty acids (SFA) and polyunsaturated fatty acids to saturated fatty acids ratio (PUFA:SFA). Male black wildebeest meat samples had higher levels of PUFA (35.0%) when compared to the female meat samples (28.9%). This differences was also reflected in a higher PUFA:SFA ratio in males when compared to the females (0.80 vs. 0.60). The pHu values of the muscles ranged from 6.50 to 6.59, which is indicative of dark, firm and dry (DFD) meat. Mean CIE L*, CIE b*, Chroma and hue angle values of the muscles ranged from 27.0-33.4, 8.0-10.2, 14.0-15.9 and 34.3-39.7, respectively. Mean cooking loss percentages and Warner-Bratzler shear force (WBSF) values of the muscles ranged from 25.9-33.5% and 3.9-6.5 kg/cm ø, respectively. The LTL and SM muscles had overall lighter appearance than other muscles. The IS muscle had the lowest cooking loss percentage while the ST muscle had the highest value. The IS and SS muscles had the lowest mean WBSF values, and can thus considered to be the most tender. The LTL muscle was further classified according to pH values; pH>6 being DFD and pH<6 being classified as normal. The DFD LTL was significantly darker in colour, and had a lower cooking loss percentage and WBSF values than normal meat. The moisture, protein, fat and ash content of the respective muscles ranged between 75.6-78.1%, 19.4-22.6%, 1.3-1.8%, and 1.1-1.3%, respectively. The SS muscle had the highest moisture content, while the LTL muscle had the lowest moisture content. The LTL muscle had the highest protein and fat content, compared to the IS muscle that had the lowest fat content. The fatty acid profile of black wildebeest muscles contained the highest level of SFA, followed by PUFA and lastly the MUFA. The IS muscle contained the highest composition (%) of SFA (68.8 ± 3.71%), whilst the ST had the lowest composition of 47.0 ± 3.70%. The SS muscle had the highest MUFA content of 20.9 ± 1.57%, compared to the IS muscle which had the lowest MUFA content of 8.1 ± 1.57%. The LTL and ST muscles had the highest PUFA content (40.0 ± 3.30% and 40.0 ± 3.29%, respectively), compared to the IS that had the lowest PUFA composition (23.0 ± 3.30%). The LTL and ST muscles had the highest PUFA:SFA ratio (1.0 ± 0.1 and 0.9 ± 0.11, respectively). The BF muscle had the highest ω-6:ω-3 of 4.5 ± 0.72, whilst the SM muscle contained the lowest ratio (1.20 ± 0.77). The effect of post-mortem ageing on the physicochemical and microbiological attributes of the LTL and BF muscles was investigated. The LTL muscle had a higher weep loss percentage (0.56%), when compared to the BF (0.38%). The TBARS value of the BF muscle was higher (1.32 mgMDA/kg meat) than that of the LTL muscle (1.11 mgMDA/kg meat). The mean pH, cooking loss percentage and Warner-Bratzer shear forces values decreased with an increase in ageing time. Mean TBARS values, total viable counts and Enterobacteriaceae counts increased with a longer ageing period. After considering the changes in the aforementioned attributes, it was concluded that black wildebeest meat should be aged for at least 12 days under chilled vacuum packaging. Black wildebeest meat microbial counts remained within the suggested limits for human consumption in this study. The meat is also characterized by a low fat content and high protein content, which make it suitable for consumption by consumers looking for healthy red meat.

AFRIKAANSE OPSOMMING: Die studie het die fisiochemies- en mikrobiologies-verwante eienskappe betreffende vleisgehalte van ses spiere [Longissimus thoracis et lumborum (LTL), Biceps femoris (BF), Infraspinatus (IS), Supraspinatus (SS), Semimembranosus (SM) en Semitendinosus (ST)] verkry van volwasse manlike en vroulike swartwildebees (Connochaetes gnou) wat uitgedun is, vasgestel. Beskrywende inligting oor die onderskeie spiere sluit in karkaseienskappe, fisiese eienskappe (pH, oppervlakkleur, drupverliespersentasie, weegverliespersentasie, kookverliespersentasie en Warner-Bratzler skeurkrag), chemiese eienskappe (vog, proteïen, vet, as, lipied oksidasie en vetsuurprofiel) en mikrobiologiese eienskappe (totale mikrobe telling en Enterobacteriaceae). Geslag- en oesjaar is as hoof-effekte in die analise van karkaseienskappe beskou, terwyl geslag en spiertipe die belangrikste effekte was in die analise van die fisio-chemiese eienskappe van al die spiere. Spiertipe en verouderingstyd was die belangrikste effekte wat oorweeg was om die invloed van veroudering op die LTL- en BF-spiere te bepaal. Die gemiddelde lewendige gewig van diere wat in 2016 geoes is, het nie verskil van dié diere wat in 2017 geoes is nie (149.5 ± 4.23 kg vs 163.4 ± 5.92kg). Manlike swartwildebeeste het 'n swaarder lewende gewig (141.4 ± 5.92 kg) en swaarder koue karkasgewig (89.8 ± 1.91 kg en 85.8 ± 1.99 kg) in vergelyking met die lewendige gewig (117.4 ± 4.23 kg) en warm en koud karkasgewig (71.0 ± 2.67kg en 68.6 ± 2.79 kg) van die vroulike swartwildebeeste gehad. Die uitslagpersentasie vir manlike swartwildebeeste (50.2 ± 0.62%) het nie verskil van die -persentasie van die vroulike diere nie (48.6 ± 0.87%). Gewigte van die tragea en longe was swaarder in die diere wat in 2017 geoes is. Swaarder vel-, kop-, tong-, poot-, hart- en miltgewigte is aangeteken vir manlike swartwildebeeste. Afval (uitgesonderd die spysverteringskanaal) het onderskeidelik 12.7% en 11.2% tot die lewende gewig van die manlike en vroulike swartwildebeeste bygedra. ‘n Betekenisvolle invloed van geslag is waargeneem in terme van die persentasie samestelling van totale poli-onversadigde vetsure (PUFA) en totale versadigde vetsure (SFA), asook die poli-onversadigde vetsure tot versadigde vetsuur verhouding (PUFA:SFA). Manlike swartwildebees vleismonsters het hoër vlakke van PUFA (35.0%) in vergelyking met die vroulike vleismonsters (28.9%) gehad. Dié verskille is ook weerspieël in 'n hoër PUFA: SFA verhouding in die vleismonsters van die manlike swartwildebeeste, wanneer vergelyk met die -monsters van die vroulike swartwildebeeste (0.80 vs. 0.60). Die pHu waardes van die onderskeie spiere het varieer tussen 6.50 en 6.59, wat aanduidend is van donker, ferm en droë (DFD) vleis. Die gemiddelde CIE L *, CIE b *, Chroma en kleurvoorkomswaardes van die spiere het onderskeidelik tussen 27.0 en 33.4, 8.0 en 10.2, 14.0 en 15.9 en 34.3 en 39.7 gevarieer. Die gemiddelde kookverliespersentasie en Warner-Bratzler skeurkrag (WBSF) waardes van die spiere het onderskeidelik van 25.9-33.5% en 3.9-6,5 kg/cm ø gewissel. Die LTL en SM spiere het ʼn algehele ligter voorkoms as die ander spiere gehad. Die IS-spier en die ST-spier het onderskeidelik die laagste en hoogste kookverliespersentasie gehad. Die IS- en SS-spiere het die laagste gemiddelde WBSF waarde gehad en kan dus as die sagste spiere beskou word. Die LTL spier is ook volgens pH-waardes geklassifiseer, met ʼn pH>6 wat as DFD en ʼn pH<6 wat as normaal geklassifiseer word. Die DFD LTL was aansienlik donkerder van kleur en het 'n laer kookverliespersentasie en WBSF waarde as die ander normaal geklassifiseerde vleismonsters gehad. Die vog-, proteïen-, vet- en as-inhoud van die onderskeie spiere het onderskeidelik tussen 75.6-78.1%, 19.4-22.6%, 1.3-1.8% en 1.1-1.3%, gewissel. Die SS- en LTL spier het onderskeidelik die hoogste en laagste voginhoud gehad. Die LTL spiere is gekenmerk deur die hoogste proteïen- en vetinhoud, in vergelyking met die IS spiere wat die laagste vetinhoud gehad het. Die vetsuurprofiel van swartwildebees spiere bevat die hoogste vlak van SFA, met medium vlakke van PUFA en lae vlakke van MUFA. Die IS-spier het die hoogste SFA samestelling (68.8 ± 3.71%) gehad, terwyl die ST die laagste samestelling van 47.0 ± 3.70% gehad het. Die SS-spier het die hoogste MUFA-inhoud van 20.9 ± 1.57%, in vergelyking met die IS-spier wat die laagste MUFA-inhoud van 8.1 ± 1.57% gehad het. Die LTL- en ST-spier het die hoogste PUFA-inhoud (onderskeidelik 40.0 ± 3.30% en 40.0 ± 3.29%)gehad, wanneer dit met die IS vergelyk is, wat die laagste PUFA-samestelling gehad het (23.0 ± 3.30%). Die LTL- en ST-spier het die hoogste PUFA: SFA verhouding (1.0 ± 0.1 en 0.9 ± 0.11, onderskeidelik) gehad. Die BF spier het die hoogste ω-6: ω-3 van 4.5 ± 0.72 gehad, terwyl die SM-spier die laagste verhouding (1.20 ± 0.77) bevat. Die effek van nadoodse veroudering op die fisio-chemiese en mikrobiologiese eienskappe van die LTL- en BF-spier is ondersoek. Die LTL spier het 'n hoër uitloogverlies persentasie (0.56%), in vergelyking met die BF (0.38%) gehad. Die TBARS-waarde van die BF-spier was hoër (1.32 mgMDA/kg vleis) as dié van die LTL spier (1.11 mgMDA/kg vleis). Die gemiddelde pH, kookverliespersentasie en Warner-Bratzer skeurwaarde het afgeneem met 'n toename in verouderingstyd. Die gemiddelde TBARS waarde, totale mikrobe - en Enterobacteriaceae tellings het met 'n toename in verouderingstydperk toegeneem. Na oorweging van die veranderinge in bogenoemde eienskappe, is die gevolgtrekking dat swart wildebees vleis vir ten minste 12 dae onder verkoelde omstandighede en vakuumverpak verouder moet word. Swartwildebees vleis mikrobe tellings in die studie was binne die voorgestelde grense vir menslike verbruik gebly. Die lae vetinhoud en hoë proteïeninhoud maak dit ook aanvaarbaar vir gebruikers wat verkies om lae-vet rooivleis te geniet.

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