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Welcome to Wine Flavor 101B: Recognizing Defects During Aging

Welcome to Wine Flavor 101B: Recognizing Defects During Aging. January 14, 2011. Overview of Potential Problems During Aging. Linda F. Bisson Department of Viticulture and Enology University of California, Davis, CA. Off-Characters Found in Wine. Can originate in vineyard

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Welcome to Wine Flavor 101B: Recognizing Defects During Aging

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  1. Welcome to Wine Flavor 101B:Recognizing Defects During Aging January 14, 2011

  2. Overview of Potential Problems During Aging Linda F. Bisson Department of Viticulture and Enology University of California, Davis, CA

  3. Off-Characters Found in Wine • Can originate in vineyard • Can derive from microbial activity • Can arise from conditions of aging

  4. Defects Arising During Aging • Microbial activity • Chemical reactions • Contaminant transfer

  5. Microbial Activity

  6. Microbial Off-Characters During Aging • Lactic acid bacteria • Acetic acid bacteria • Spoilage yeasts • Film formers • Residual sugar utilizers • Survivalists

  7. Microbial Off-Characters During Aging • Off-odors, off-tastes, off-colors, hazes, films, precipitates and sediments • Direct synthesis • Loss of aroma characters: microbial suppression or buffering • Microbial modification of grape characters • Microbial end products as reactants

  8. Microbial Off-Odors • S-compounds • Aldehydes • Vinyl phenols • Amino acid derivatives • Grape compound metabolites

  9. Microbial Off-Tastes • Sourness • Bitterness • Slimy (okra) finish

  10. Microbial Off-Colors • Pink • Orange

  11. Hazes, Films, Precipitates and Sediments • Result of microbial biomass/biofilm • Production of polysaccharides • Production/modification of tannin-interacting components • Visual or gritty

  12. Chemical Reactions

  13. Chemical Off-Characters During Aging • Unmasking vineyard defect • Dependent upon microbial end products • Oxidation-reduction driven

  14. Unmasking Vineyard Defect • Loss of aromatic esters • Degradation of grape glycosides and loss of volatiles and aging potential

  15. Off- Characters Dependent Upon Microbial End Products • Masking due to aldehyde/higher alcohol formation • Production of chemically reactive components: diacetyl • Production or modification of redox reactants or redox potential

  16. Oxidation-Reduction Condition • Redox reactions refer to transfer of electrons • Chemical reactions can both consume or release electrons • The impact of oxygen in wine is due to chemical reactivity and the tendency to pick up electrons

  17. Contaminant transfer

  18. Contaminant Transfer • From corks • From oak • From winery flora

  19. Contaminant Transfer from Corks AWRI: • Trichloroanisole (TCA; cork taint) • 2-Methoxy 3,5-dimethylpyrazine (MDMP) • Host of other off-characters can be derived from cork

  20. Contaminant Transfer from Oak Chatonnet: • TCA • 2-Methoxy 3,5-dimethylpyrazine (MDMP) • Host of other compounds depending upon how barrel is made and oak is treated

  21. From Winery Flora • TCA • MDMP • Geosmin • Compounds made by winery flora (molds and bacteria) can be absorbed into the wine

  22. Today’s Program • Chemical Issues During Aging • Spoilage by Acetic Acid Bacteria • Yeast Spoilage • Emphasis: Brettanomyces

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