Masters Degrees (Food Science)
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- ItemClimatic region and vine structure : effect on pinotage wine phenolic composition, total antioxidant capacity and colour(South African Society for Enology and Viticulture, 2006) De Beer, D.; Joubert, E.; Marais, J.; Van Schalkwyk, D.; Manley, M.The phenolic composition, total antioxidant capacity (TAC) and colour of Pinotage wines of the 2001, 2002 and 2003 vintages were investigated, using spectrophotometric, high-performance liquid chromatography (HPLC), free radical scavenging and objective colour analyses. Grapes were harvested from grapevines in three climatic regions ranging from cool to warm, with bush (20- and 30-cm trunk height) and trellised (30- and 60-cm trunk heights) vine treatments, on several vineyard sites in each climatic area. Climatic region had a significant effect on the content of several phenolic compounds; the concentration of anthocyanin monoglucosides, flavonols, flavan-3-ols and tartaric acid esters of hydroxycinnamic acids generally increased as the climatic region becomes cooler, while concentrations of acylated derivatives and free hydroxycinnamic acids decreased. Wines made from bush vines contained higher concentrations of flavonols, gallic acid and flavan-3-ols than those from trellised vines, but lower concentrations of some anthocyanin monoglucosides and acylated derivatives, as well as non-coloured polymers. These trends resulted in differences in TAC and objective colour parameters, although the different vintages did not show the same trends in all cases. More vintages should therefore be investigated to clarify these effects. Wines from the cool climatic regions and from bush vines were generally darker coloured, with higher TAC than those from the warm climatic regions and bush vines, respectively. High TAC, therefore, coincided with higher colour quality. Variations in TAC were partly explained by trends for individual phenolic compounds, although unknown compounds played a major role.
- ItemPhenolic compounds : a review of their possible role as in vivo antioxidants of wine(South African Society for Enology and Viticulture, 2002) De Beer, D.; Joubert, E.; Gelderblom, W. C. A.; Manley, M.Phenolic compounds are a large and complex group of chemical constituents found in red and white wines which not only affect their quality, but also contribute to their beneficial health effects. The antioxidant properties of phenolic compounds are important in determining their role as protective agents against free radical-mediated disease processes. This review discusses the principles of oxidative stress and the resultant cellular damage caused by lipid peroxidation in vivo. Different groups of wine phenolic compounds are detailed, with specific reference to their in vitro antioxidant activity and their relative potency as free radical scavengers. The absorption and bioavailability of phenolic compounds from dietary sources is discussed.