The authentication of regionally unique South African lamb

Erasmus, Sara Wilhelmina (2017-03)

Thesis PhD(Food Sc)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: Noted for its unique herbaceous flavour which is imbued from a diet of indigenous fragrant plants, Karoo lamb is marketed as one of South Africa’s finest meat products. It is also the first fresh meat product to receive Protected Geographical Indication (PGI) status in South Africa. Its distinct quality is imparted through natural grazing of the sheep on the Karoo veld of the Northern parts of the country. Although it is considered common knowledge to South Africans that Karoo lamb is different to that of lamb meat from other regions, there is a lack of scientific evidence to verify these claims. In order for Karoo lamb to receive official recognition and protection as an authentic product, it is vital to confirm such claims. The aim of the study was to validate the authentic nature of regionally unique South African lamb using analytical techniques. Emphasis was placed on Karoo lamb, while the characteristics of other region of origin lamb, such as the Rûens and Free State lamb, were also determined. A key aspect of the study was to link the characteristic diet, related to its origin, to the sensory and chemical profiles of the meat and fat. The findings show that diet plays an integral part in the sensory characteristics of Karoo lamb meat and hence, have a significant influence on the sensory and chemical profile of South African lamb. Descriptive sensory analysis (DSA), fatty acid analysis, solid-phase microextraction (SPME), isotope ratio mass spectrometry (IRMS), near-infrared reflectance spectroscopy (NIRS) (using a portable MicroNIR spectrometer) and proton transfer reaction-mass spectrometry (PTR-MS) proved to be very successful analytical tools for the authentication of lamb, distinguishing Karoo from Non-Karoo lamb. A key finding was the detection of volatiles, specifically terpenes, present in both the Karoo bushes and the Karoo lamb meat and fat. Terpenes were prominent in the fat tissue and detected at mass ratios m/z 81 and m/z 137 using PTR-MS. The dominant terpenes were tentatively identified as α-pinene, β-pinene, limonene and trans-caryophyllene using SPME. The highest concentrations of terpenes were detected in Karoo lamb, while the Non-Karoo lamb did not or hardly contained any. Within the Karoo, regional differences were apparent as Hantam Karoo lamb had the highest ratings for herbaceous aroma and flavour and contained the greatest concentration of terpenes. Therefore, it is proposed that Karoo lamb is marketed according to its region of origin. Herbaceous aroma and flavour attributes associate with a diet rich in fragrant Karoo plants which were verified with stable isotope ratio analysis. The stable isotopic ratios were indicative of the extensive grazing diet of the animals where discrimination between diets composed of grass, Karoo bushes, lucerne/alfalfa (Medicago sativa) and a combination of grass and Karoo bushes were achieved. The results confirm that Karoo bushes are responsible for the distinct aroma and flavour of Karoo lamb. Hence, the results serve as evidence for its certification and justify the protection of its indicator status. It is recommended that the meat industry utilise the value linked to origin and invest in the marketing of regionally unique lamb. In order to prevent fraudulence and the misuse of protected names, the meat industry should also implement NIRS and PTR-MS as a rapid and effective origin based testing method. The combination of these two techniques improves the discriminative power and allows reliable origin classification.

AFRIKAANSE OPSOMMING: Bekend vir sy unieke kruidagtige geur, neergelê deur ‘n dieet ryk aan inheemse geurige plante, word Karoolam as een van Suid-Afrika se top vleisprodukte bemark. Karoolam is die eerste vars vleisproduk in Suid-Afrika om die status van beskermde geografiese aanduiding (Protected Geographical Indication; PGI) te ontvang. Die unieke kwaliteit van Karoolam word veroorsaak deur die natuurlike weiding van skape op die Karooveld in the noordelike dele van Suid-Afrika. Alhoewel dit vir die Suid-Afrikaanse verbruiker algemene kennis is dat Karoolam verskil van lamsvleis uit ander produksiestreke, is daar 'n gebrek aan wetenskaplike navorsing om hierdie stellings te verifieer. Dit is egter noodsaaklik om hierdie aansprake te bevestig sodat Karoolam amptelike erkenning en beskerming kan ontvang as 'n unieke produk. Die doel van die studie was om die outentieke aard van streeks-unieke Suid-Afrikaanse lamsvleis te bekragtig deur die gebruik van analitiese tegnieke. Daar is veral klem gelê op Karoolam, maar die eienskappe van ander streeks-unieke lamsvleis, soos dié van Rûens en Vrystaatse lam, is ook bepaal. 'n Belangrike aspek van die studie was om die kenmerkende dieet, verbind met die oorsprong, aan die sensoriese en chemiese profiele van die vleis en vet te koppel. Daar is gevind dat die dieet ‘n integrale rol speel in die sensoriese eienskappe van Karoolam vleis en gevolglik 'n beduidende invloed het op die sensoriese en chemiese profiel van Suid-Afrikaanse lam. Beskrywende sensoriese analise, vetsuur ontledings, soliede fase mikro-ekstraksie (SPME), isotoop verhouding massa spektrometrie (IRMS), naby-infrarooi reflektansie spektroskopie (NIRS) (met behulp van 'n draagbare MicroNIR spektrometer) en proton oordrag reaksie-massa spektrometrie (PTR-MS) is bewys as suksesvolle analitiese tegnieke vir die verifikasie van die unieke aard van lamsvleis met betekenisvolle onderskeid tussen Karoolam en Nie-Karoolam. ‘n Betekenisvolle bevinding was die deteksie van vlugtige komponente, bekend as terpene, in die Karoo bossies, asook die Karoolam vleis en vet. Hierdie terpene was veral volop in die vetweefsel en is opgetel by massa verhoudings van m/z 81 en m/z 137 met behulp van PTR-MS. Dominante terpene is tentatief geïdentifiseer as α-pineen, β-pineen, limoneen en trans-caryophyllene met behulp van SPME. Die hoogste konsentrasies van terpene is gevind in Karoolam, terwyl die Nie-Karoolam geen of ‘n lae konsentrasie bevat. Streeksverskille het in die Karoo voorgekom met die hoogste graderings vir kruidagtige aroma en geur en konsentrasie van terpene vir Hantam Karoolam. Daarom word daar voorgestel om Karoolam volgens sy streek van herkoms te bemark. Kruidagtige aroma en geureienskappe assosieer met 'n dieet ryk aan geurige Karoo plante wat uiteraard ook deur die stabiele isotoop verhoudings geverifieer is. Die ekstensiewe dieet van die skape is deur die stabiele isotoop verhoudings weerspieël waar onderskeiding getref kon word tussen diëte wat bestaan uit gras, Karoo bossies, lusern (Medicago sativa) en 'n kombinasie van gras en Karoo bossies. Die resultate bevestig dat Karoo bossies verantwoordelik is vir die kenmerkende geur en geur van Karoolam. Die resultate dien dus as bewys vir die sertifisering en beskerming van Karoolam as ‘n unieke produk. Die vleisbedryf word aanbeveel om die waarde wat aan oorsprongname gekoppel word, te benut en sodoende te belê in die bemarking van streeksunieke lamsvleis. Die vleisbedryf kan ook NIRS en PTR-MS implementeer as vinnige en doeltreffende oorsprong gebaseerde analitiese metodes om die misbruik van beskermde name te voorkom. Die kombinasie van hierdie twee tegnieke verbeter die onderskeidingsvermoë en dra by tot betroubare oorsprong klassifikasie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101031
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