The chemical profiling of boar taint within entire male pigs in the Western Cape, South Africa

Bussmann, Karla (2015-12)

Thesis (MSc Food Sc)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: The objective of this study was to investigate whether there were correlations between sections of the South African PORCUS classification system and the intramuscular fat percentage of the Longissimus dorsi muscle of entire male carcasses, as well as between the classification system and androstenone concentration found in the subcutaneous backfat of the carcass. Furthermore it was investigated if androstenone in the subcutaneous fat of the Longissimus thoracis would increase or decrease due to the use of three different cooking methodologies (pan fried, oven baked and sous vide). In the first trial, the Longissimus dorsi of P-, O- and R-classified entire male carcasses (44 P-, 82 O- and 46 R-carcasses) underwent chemical composition- and androstenone concentration (HPLC-MS/MS-FD) analyses. It was expected that as the PORCUS classes decreased in percentage lean meat, both the intramuscular fat (determined with the use of chemical analysis) and androstenone concentration (μg/g) would increase. However in this study no differences were found in the intramuscular fat percentage of P- and O-carcasses or P- and R-carcasses (P > 0.05). R-classified carcasses had a higher intramuscular fat percentage than that of O-carcasses (p < 0.001). These results therefore indicated that there was no specific trend that the intramuscular fat percentage correlates with the lean meat percentage as predicted by the PORCUS classification. Also, there was no correlation (r = 0.065; p = 0.397) between the intramuscular fat percentage and backfat thickness (as determined by the Hennessey grading probe). It was also found that there was no significant difference between androstenone found in the intramuscular fat of P-, O- or R carcasses (P > 0.05). This was also contrary to what was expected. It could thus not be claimed that as the % lean meat yield according to the PORCUS classification decreases, the androstenone concentration would increase. There was, however, a significant but low correlation between increasing warm carcass weight (kg) and increasing androstenone concentrations (μg/g) (r = 0.2674; p < 0.01). Further investigation also indicated that O-carcasses had the highest percentages of carcasses (30.12%) with androstenone levels above the sensory threshold (androstenone > 0.45 μg/g). In the second research trial, different cooking methods (pan fried, oven baked and sous vide) of 12 pork chops (Longissimus thoracis) having a high predetermined androstenone concentration were compared to determine how androstenone would react to different cooking methods. All samples used were from O-classified entire male pig carcasses as this carcass classification group was readily available and it was shown that they had higher concentrations of androstenone present within the subcutaneous fat. Androstenone concentrations in the subcutaneous fat were measured before and after preparation. Pan fried chops had a significantly lower concentration of androstenone than oven baked chops (p = 0.046) which could have resulted from the different heating methods (direct dry heat and indirect dry heat, respectively) used. No difference was found in androstenone concentrations between raw samples and any of the prepared samples (P > 0.05). It is important to note that the means of all samples were above the sensory threshold (> 0.45 μg/g) which could result in consumers experiencing off odours whilst preparing pork. This could possibly have a negative effect on the pork industry.

AFRIKAANSE OPSOMMING: Die doel van die studie was om die PORCUS karkas-klassifikasie-sisteem wat in Suid-Afrika gebruik word te bestudeer en te bepaal of die verwagte korrelasies tussen die klassifikasie groepe en die intramuskulêre vet, asook die konsentrasie androstenoon in die onderhuidse vet (op die Longissimus dorsi) van die karkasse bestaan. Verder is daar vasgestel hoe androstenoon in die onderhuidse vet van die Longissimus thoracis reageer met drie verskillende gaarmaakmetodes (panbraai, oondbraai en sous vide). In die eerste proef was die chemiese samestelling asook androstenoon konsentrasies (HPLC-MS/MS-FD) van P-, O- en R-geklassifiseerde intakte manlike karkasse (44 P-, 82 O- en 46 R-karkasse) bepaal. Daar was verwag dat, soos die persentasie maer vleis binne die PORCUS klassifikasies afneem, beide die intramuskulêre vet konsentrasie en androstenoon konsentrasie sou toeneem. In hierdie studie was daar egter geen verskil tussen die intramuskulêre vet konsentrasies van P- en O-karkasse of P- en R-karkasse nie (P > 0.05). R-karkasse het wel ‘n hoër intramuskulêre vet konsentrasie gehad as die O-karkasse (p < 0.001). Die resultate dui daarop dat die verwagte patroon van verhoogte maervleis opbrengste soos voorspel deur die PORCUS klassifikasie nie tot laer intramuskulêre vet konsentrasies gelei het nie. Verder was daar ook geen korrelasie (r = 0.065; p = 0.397) tussen intramuskulêre vet konsentrasies en rugvetdikte gevind nie. Daar was ook geen verskil tussen die konsentrasies van androstenoon in die onderhuidse rugvet en die verskillende PORCUS groepe nie (P > 0.05). Dit was verwag dat soos die PORCUS klassifikasie groepe daal in persentasie maervleis, so sou die konsentrasie androstenoon styg, dit is egter nie in hierdie studie bewys nie. Daar was wel ‘n korrelasie tussen die toename in warm karkas massa (kg) en toename in androstenoon konsentrasies (μg/g) (r = 0.267; p < 0.01). Verdere ondersoeke het getoon dat O-karkasse die hoogste persentasie karkasse (30.12%) met androstenoon konsentrasies bo die sensoriese waarnemings limiet getoon het (androstenoon > 0.45 μg/g). In die tweede proef is die effek van drie verskillende gaarmaakmetodes op die androstenoon konsentrasie teenwoordig in onderhuidse vet van 12 varktjop monsters (Longissimus thoracis) ondersoek. Alle monsters was afkomstig van O-geklassifiseerde intakte manlike karkasse. Androstenoon konsentrasies in die onderhuidse vet was bepaal voor en na gaarmaak. Daar is gevind dat monsters wat in die pan gaargemaak is laer konsentrasies androstenoon getoon het as monsters wat in die oond gaargemaak is (p = 0.046). Die resultaat is moontlik as gevolg van die verskillende maniere waarop die gaarmaakmetodes funksioneer (die pan maak gebruik van direkte droë hitte terwyl die oond indirekte droë hitte gebruik). Daar was verder geen verskil tussen rou monsters en oorstemmende gaar monsters nie (P > 0.05). Dit is belangrik om daarop te let dat die gemiddelde androstenoon konsentrasie van alle monsters bo die sensoriese waarnemings limiet was (androstenoon > 0.45 μg/g). Die hoë konsentrasie kan lei tot onaangename kookervarings deur die androstenoon sensitiewe verbruiker, wat uiteindelik ’n negatiewe effek kan hê op die varkvleis industrie.

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