Browsing by Author "Van Rooyen, T. J."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Biological deacidification of musts induced by yeasts or malolactic bacteria and the effect on wine quality
    (South African Society for Enology and Viticulture, 1987) Van Rooyen, T. J.; Tracey, R. P.
    This study investigated the possible use of Schizosaccharomyces pombe and Schizosaccharomyces malidevorans for deacidification of red wines during alcoholic fermentation, in comparison with existing deacidification practices of induced or spontaneous malolactic fermentation (MLF) in South Africa. In red must, the effect of these yeasts on alcoholic fermentation rate, rate of L-malic acid removal, as well as the effect of mixed cultures with Saccharomyces cerevisiae at different inoculum concentrations and sizes of inocula on wine quality was investigated. In white must, the effect of pure culture inocula and temperature on wine quality and production of volatile bouquet substances was also studied. Both Schizosaccharomyces spp. were found to deacidify normal concentrations of L-malic acid in musts effectively at higher growth temperatures, but the ability of Schiz. pombe was inhibited by high concentrations of Lmalic acid which was not pH dependent. Certain key volatile fermentation bouquet compounds were produced in very low quantities, which seems to be the reason for poor sensory quality wines produced by Schizosaccharomyces.
  • Thumbnail Image
    Item
    A rapid and quantitative HPLC method for determination of diethylene glycol
    (South African Society for Enology and Viticulture, 1986) Van Rooyen, T. J.; Van Wyk, C. J.
    A method was developed for determining diethylene glycol (DEG) by HPLC. Good separation was achieved by analysis of standard mixtures containing normal wine components and DEG. Addition of DEG to wine samples proved that DEG did not elute with any of the known constituents. Recovery studies proved the method to have a good repeatability. A selection of South African and imported wines were analysed and it was found that none contained any DEG.