The authentication of regionally unique South African lamb

[摘要] 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.

[发布机构] Stellenbosch University