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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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overview of potential problems during aging

Overview of Potential Problems During Aging

Linda F. Bisson

Department of Viticulture and Enology

University of California, Davis, CA

off characters found in wine
Off-Characters Found in Wine
  • Can originate in vineyard
  • Can derive from microbial activity
  • Can arise from conditions of aging
defects arising during aging
Defects Arising During Aging
  • Microbial activity
  • Chemical reactions
  • Contaminant transfer
microbial off characters during aging
Microbial Off-Characters During Aging
  • Lactic acid bacteria
  • Acetic acid bacteria
  • Spoilage yeasts
    • Film formers
    • Residual sugar utilizers
    • Survivalists
microbial off characters during aging1
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
microbial off odors
Microbial Off-Odors
  • S-compounds
  • Aldehydes
  • Vinyl phenols
  • Amino acid derivatives
  • Grape compound metabolites
microbial off tastes
Microbial Off-Tastes
  • Sourness
  • Bitterness
  • Slimy (okra) finish
hazes films precipitates and sediments
Hazes, Films, Precipitates and Sediments
  • Result of microbial biomass/biofilm
  • Production of polysaccharides
  • Production/modification of tannin-interacting components
  • Visual or gritty
chemical off characters during aging
Chemical Off-Characters During Aging
  • Unmasking vineyard defect
  • Dependent upon microbial end products
  • Oxidation-reduction driven
unmasking vineyard defect
Unmasking Vineyard Defect
  • Loss of aromatic esters
  • Degradation of grape glycosides and loss of volatiles and aging potential
off characters dependent upon microbial end products
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
oxidation reduction condition
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
contaminant transfer1
Contaminant Transfer
  • From corks
  • From oak
  • From winery flora
contaminant transfer from corks
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
contaminant transfer from oak
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
from winery flora
From Winery Flora
  • TCA
  • MDMP
  • Geosmin
  • Compounds made by winery flora (molds and bacteria) can be absorbed into the wine
today s program
Today’s Program
  • Chemical Issues During Aging
  • Spoilage by Acetic Acid Bacteria
  • Yeast Spoilage
  • Emphasis: Brettanomyces