Browsing by Author "Mansfield, A. K."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Effect of fermentation, postfermentation, and postbottling heat treatment on Cabernet Sauvignon glycoconjugates
    Mansfield, A. K.; Zoecklein, Bruce W. (American Society for Enology and Viticulture, 2003)
    In Cabernet Sauvignon must, total and phenol-free glycosides (expressed as glycosyl-glucose) rose during fermentation while skin concentrations dropped. Wines were heated postfermentation, prior to dejuicing (rising 2 to 3degreesC per day from 23 to 42degreesC, and held for one day at 42degreesC), or after bottling (at 42degreesC for 21 days) to determine the effect on total glycosides, glycosidic fractions, and anthocyanin complexing. Pre-dejuicing thermal vinification resulted in higher total (12%) and phenol-free (18%) glycosides. Large polymeric pigments rose 208% and small polymeric pigments rose 41%. Skins had lower total glycosides (-16%), and no significant difference in phenol-free glycosides. Postbottling heat treatment resulted in lower total (-15%) and phenol-free (-16%) glycosides, and increased hue (25%). Large polymeric pigments increased 62% compared to control wines.
  • Thumbnail Image
    Quantification of glycosidase activity in selected strains of Brettanomyces bruxellensis and Oenococcus oeni
    Mansfield, A. K.; Zoecklein, Bruce W.; Whiton, R. S. (American Society for Enology and Viticulture, 2002)
    Brettanomyces bruxellensis and lactic acid bacteria are common microorganisms capable of modifying wine aroma and flavor. The activity of beta-glucosiclase against p-nitrophenyl-beta-D-glucopyranoside was determined in a model system for 14 strains of Brettanomyces bruxellensis yeast and 9 strains of lactic acid bacteria (Oenococcus oeni). All Brettanomyces strains and 7 Oenococcus strains exhibited enzymatic activity against this substrate. B. bruxellensis beta-glucosiclase activity was primarily intracellular; O. oeni showed some extracellular activity. Strains showing activity greater than 1000 nmole mL(-1) g dry cell mass(-1) 24 hr(-1) for Brettanomyces, or 100 nmole mL(-1) g dry cell mass(-1) 24 hr(-1) for Oenococcus, were evaluated for their effect on native Viognier grape glycosides. Neither genus was active on Viognier grape glycosides.