Browsing by Author "Du Toit, W."
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- ItemCharacterisation of pinotage wine during maturation on different oak products(SASEV, 2008-01) De Beer, D.; Joubert, E.; Marais, J.; Du Toit, W.; Fourie, B.; Manley, M.The effect of oak contact on the phenolic composition, total antioxidant capacity (TAC) and colour of Pinotage wines was investigated during maturation. Oak maturation included traditional treatments, such as new, second-fill and third-fill barrels, as well as alternative treatments (oak chips, staves, extract and dust) applied in old barrels over a period of 28 weeks. Oak maturation using traditional and alternative treatments improved the objective colour of Pinotage wine by decreasing the L* value. Losses in TAC caused by decreased concentrations of monomeric phenolic compounds (most anthocyanins, flavan-3-ols, flavonols and hydroxycinnamic acids) during oak maturation were negated by increased concentrations of gallic acid and the formation of new oligomeric and polymeric pigments. Wine maturation in stainless steel containers also resulted in a decrease in anthocyanin content. The decrease in phenolic acid content for wines matured in stainless steel was less pronounced, while their flavan-3-ol content remained stable. The new-barrel treatment had the most pronounced effect on all parameters. Oak maturation can be used for the production of Pinotage wine when the retention of TAC is a high priority.
- ItemDietary management of people with diabetes mellitus : Association for Dietetics in Southern Africa (ADSA)(Health and Medical Publishing Group (HMPG), 1997-10) Badenhorst, A. M.; Badham, J.; Blaauw, Renee; Dannhauser, A.; Du Toit, W.; Herbert, C.; Johnson, J.; Joubert, P. A.; Menssink, E.; Peberdy, C.; Silvis, N.; Slabber, M.; Wilson, R.AIM: The aim of these recommendations is to encourage a uniform approach to the nutritional management of diabetes in South Africa. Although the implementation of these recommendations will vary according to intake of traditional, ethnic and cultural foods, these recommendations apply to all population groups, and should be tailored to individual needs, circumstances and preferences.
- ItemThe effect of grape temperature on the sensory perception of Méthode Cap Classique wines(South African Society for Enology and Viticulture, 2017) Mafata, M.; Buica, A. S.; Du Toit, W.; Panzeri, V.; Van Jaarsveld, F. P.The production process of South African bottle-fermented sparkling wine, the Méthode Cap Classique (MCC), follows the traditional French method (méthode champenoise), although each cellar has its own unique additions to the method. South African winemakers use different techniques and blends to achieve their award-winning MCCs, but there have not been many scientific investigations of the science behind these wines. This project is one of the first scientific studies on MCC. MCC wines were made using Chardonnay and Pinot Noir grapes harvested over two vintages (2014 and 2015) from two regions (Robertson and Darling) and stored at 0°C, 10°C, 25°C and 30°C before processing. The study was aimed at investigating the effect of grape storage temperature on the sensory characteristics of MCCs. The aroma and taste of the final nine-month old MCCs were evaluated, with each region analysed separately. The study showed a grouping of the MCCs according to temperature treatments for both vintages. There were vintage differences in terms of the attributes cited and the frequency of citations. Based on the frequency of citation, the MCCs made 2014 from grapes stored at 0°C and 10°C were described by the judges as having a fruity, fresh and crisp aroma, whilst those made from grapes stored at 25°C and 30°C were described as having oxidised fruit, volatile acidity and solvent-like aromas. The judges perceived less oxidation and volatile acidity (VA) (in terms of the frequency of citation) in the aroma of the 2015 MCCs, although treatments at higher temperatures were still associated with less desirable attributes compared to treatments at lower temperature. This study shown that the temperature of the grape at the time of processing has a significant effect on the aroma of MCCs aged nine months, and not so much of an effect on the taste.
- ItemInteraction effects of 3-mercaptohexan-1-ol (3MH), linalool and ethyl hexanoate on the aromatic profile of South African dry Chenin Blanc wine by descriptive analysis (DA)(South African Society for Enology and Viticulture, 2018) Wilson, C.; Brand, J.; Du Toit, W.; Buica, A. S.Interaction studies are some of the most interesting sensory experiments that highlight the effect of composition on wine perception. The use of single compounds, viz. an ester (ethyl hexanoate), a terpene (linalool) and a thiol (3-mercaptohexanol, 3MH), which have previously been shown to be representative of Chenin Blanc wines, resulted in typical descriptors for these compounds, such as ‘apple, ‘floral’ and ‘guava’ respectively. Interaction effects were observed between the compounds, and these were reflected in both the nature and the level of attributes generated. Additionally, interaction effects between the compounds (singles and combinations) and the wine matrix indicated that the latter plays an important role in the perception of wine aromas. The use of a dearomatised neutral wine base added an extra dimension to this study, which usually is done in a simpler matrix, such as a model wine.
- ItemNitrogen and Sulphur Foliar Fertilisation(South African Society for Enology and Viticulture, 2019) Bruwer, F. A.; Du Toit, W.; Buica, A.The effects of fertilisation can reverberate from grapes through to wines. In wine, non-volatile compounds mainly influence the taste and flavour of wines, while volatile compounds play an important role in the aromatic expression. This review includes information on the presence of non-volatile and volatile compounds reportedly affected by nitrogen and sulphure foliar fertilisation, (bio)synthesis, and evolution throughout winemaking, their chemical properties, and their implications. The second part presents the status of the research on elucidating the influence and contribution of foliar fertilisation practices on the chemical compounds throughout winemaking, from the grape to the wine.