Title page for ETD etd-07262001-172630


Type of Document Master's Thesis
Author Mansfield, Anna Katharine
URN etd-07262001-172630
Title The effects of post-fermentation and post-bottling heat treatment on Cabernet Sauvignon (V. vinifera L.) glycosides and quantification of glycosidase activities in selected strains of Brettanomyces bruxellensis and Oenococcus oeni.
Degree Master of Science
Department Food Science and Technology
Advisory Committee
Advisor Name Title
Zoecklein, Bruce W. Committee Chair
Eigel, William N. III Committee Member
Marcy, Joseph E. Committee Member
Keywords
  • Glycosides
  • hydrolysis
  • thermal vinification
  • glycosidases
  • Brettanomyces bruxellensis
  • Oenococcus oeni
  • Cabernet Sauvignon
  • aglycone
  • lactic acid bacteria
Date of Defense 2001-06-19
Availability unrestricted
Abstract
Thermal processing has been used as a means of modifying the sensory aspects of wine. Cabernet Sauvignon wines were heated prior to dejuicing (3ºC per day from 25ºC to 42ºC) or after bottling (42ºC for 21 days) to determine the effects on total glycosides and glycosidic fractions. Total and phenol-free glycosidic concentrations in the wine and skins were quantified by analysis of glycosyl-glucose. Pre-dejuicing thermal vinification resulted in higher total glycosides (12%), phenol-free glycosides (18%), total hydroxycinnamates (16%), large polymeric pigments (LPP) (208%) small polymeric pigments (SPP) (41%), and lower monomeric pigments (42%) in wines. Skins had lower total glycosides (-16%), and no significant difference in phenol-free glycosides. Post-bottling heat treatment resulted in lower total (-15%) and phenol-free (-16%) glycosides, increased hue (25%), a 62% increase in LPP and a 29% decrease in monmeric pigments.

A second study investigated the potential of enological spoilage microorganisms to affect wine aroma, flavor, and color. The activities of b-glucosidase were determined in model systems for fourteen strains of Brettanomyces bruxellensis yeast and nine strains of lactic acid bacteria (Oenococcus oeni). All Brettanomyces strains and seven Oenococcus strains exhibited enzymatic activity. B. bruxellensis b-glucosidase activity was primarily intracellular; O. oeni showed some extracellular activity. Yeasts and bacteria showing activity greater than 1000 nmole mL-1 g -1 for Brettanomyces, or 100 nmole mL-1 g -1 for Oenococcus, were evaluated for their effect on Viognier grape glycosides. Neither was active on native grape glycosides.

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