Browsing by Author "Tromp, A."

Now showing 1 - 3 of 3
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    Chenin blanc wine volatiles and the intensity of a guava-like flavour
    (South African Society for Enology and Viticulture, 1982) Van Rooyen, P. C.; De Wet, P.; Van Wyk, C. J.; Tromp, A.
    A guava-like flavour occurring in some South African Chenin blanc and Colombard dry white wines was investigated. Headspace volatiles of some of these wines, as well as those of fresh guava fruits, were analysed by means of a gas chromatograph equipped with a "sniffer-detector". In contrast to the headspace concentrate of guava fruits, no single fraction with a typical guava flavour was found in the wines analysed. The pattern recognition system "ARTHUR" was therefore used to investigate relationships between the more important wine volatiles and the intensity of a guava-like flavour of a set of wines originating from the same Chenin blanc must. Sensory scores for this flavour were used in both category and continuous property analysis in each case. Category and correlation to property plots were used to elucidate the results. Several promising variables and ratios between variables were singled out for further investigation, notably ethyl butyrate and the ratios ethyl butyrate/ethyl decanoate and ethyl butyrate/ethyl octanoate.
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    Relationship between ergosterol concentrations in wine yeast and sugar fermentation at different temperatures
    (South African Society for Enology and Viticulture, 1989) Venter, J. J.; Van Vuuren, H. J. J.; Tromp, A.; Randall, J. H.
    The effect of cellular ergosterol on the fermentation ability of four different Saccharomyces cerevisiae wine yeast strains was studied. F~rmentations were carried out at three temperatures and ergosterol concentrations determined at six fermentation stages. The lower ergosterol concentrations at the higher temperatures are ascribed to the higher growth rate of the yeast cells resulting in a more rapid dilution of the ergosterol. Growth of yeast during fermentation was linked with the ergosterol content of the cells. The ergosterol concentration of the yeast cells was not directly correlated to specific fermentation rates.
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    Relationship between fatty acid concentrations in wine yeasts and sugar fermentation at different temperatures
    (South African Society for Enology and Viticulture, 1989) Venter, J. J.; Van Vuuren, H. J. J.; Tromp, A.; Randall, J. H.
    The effects of temperature and fermentation stage on the cellular concentrations of unsaturated and saturated fatty acids on the fermentation abilities of four different Saccharomyces cerevisiae wine yeasts were studied at three temperatures. The total unsaturated and saturated fatty acid concentrations were determined at six fermentation stages. Unsaturated fatty acid concentration decreased and the concentration of saturated fatty acids increased as fermentation proceeded. Saturated fatty acid concentration of the yeast cells correlated positively with high specific fermentation rates during the later stages of fermentation in contrast to the belief that fluid membranes with high unsaturated fatty acid concentrations enhance ethanol tolerance and, therefore, fermentation performance.