Browsing by Author "Stander, M. A."
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- ItemMammalian exocrine secretions XVII : chemical characterization of preorbital secretion of male suni, Neotragus moschatus(Springer Verlag, 2002-01) Stander, M. A.; Burger, B. V.; Le Roux, M.Gas chromatographic and gas chromatographic-mass spectrometric techniques were employed to identify 83 compounds, including alkanes, alkenes, aldehydes, 2-methylalkanes, carboxylic acids, 1-alkyl formates and alken-1-yl formates, benzoic acid, and cholesterol, in the preorbital secretion of the male suni, Neotragus moschatus. Dimethyl disulfide derivatization and lithium aluminum hydride reduction were used to determine the position of double bonds and to confirm the identity of the functional groups in some of the constituents of the secretion.
- ItemQuantitative survey of 3-alkyl-2-methoxypyrazines and first confirmation of 3-ethyl-2-methoxypyrazine in South African Sauvignon blanc wines(South African Society for Enology and Viticulture, 2013) Alberts, P.; Kidd, M.; Stander, M. A.; Nieuwoudt, Helene; Tredoux, A. G. J.; De Villiers, A. J.3-Alkyl-2-methoxypyrazines are important aroma components in Sauvignon blanc wine, contributing to the typical vegetative character associated with the cultivar. The analysis of methoxypyrazines is highly challenging and, as a result, limited quantitative data are available for South African Sauvignon blanc wines. In this study, liquid chromatography-tandem mass spectrometry was applied for the sensitive quantification of the three principal methoxypyrazines in 881 South African Sauvignon blanc wines. The total wine methoxypyrazine concentration exceeded the combined recognition threshold for the vegetative aroma in more than 60% of the samples, demonstrating the involvement of these compounds in the typical aroma of the cultivar. The analytical method was adapted to allow the accurate quantitation and spectral confirmation of 3-ethyl-2-methoxypyrazine in Sauvignon blanc wines for the first time. Concentrations ranged between 1.1 and 4.9 ng/L. Statistically significant relationships between wine methoxypyrazine concentrations and parameters related to the maturity of the grapes and to the climate, as well as geographical origin and vintage, were found.
- ItemSurvey of ochratoxin A in South African wines(South African Society for Enology and Viticulture, 2002) Stander, M. A.; Steyn, P. S.The mycotoxin, ochratoxin A (OTA), an important nephrotoxin, teratogen and carcinogen, is mainly produced as a secondary metabolite of Aspergillus and Penicillium species. The mycotoxin is a common contaminant of various feedstuffs and of foodstuffs such as grains, coffee and wine. The levels of OTA have been established in 122 South African wines, representative of a variety of wine cultivars from various wine-producing regions of the country. The method of analysis was based on the method of Visconti et al. (1999): it consisted of immunoaffinity clean up, quantification on reversed phase HPLC with fluorescence detection and confirmation of the presence of OTA by synthesising its methyl ester. The levels of OTA of most of the red and white wines were substantially lower than the maximum permissible levels of OTA in wines, as suggested by the European Union. However, high levels of OTA were found in a few noble late harvest wines. This first comprehensive survey unambiguously shows that OTA presents no cause for concern to the South African wine industry.