Transcript Welcome to Wine Flavor 101A

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
 Can derive from microbial activity
 Can arise from conditions of aging
Defects Arising During Aging
 Microbial
activity
 Chemical reactions
 Contaminant transfer
MICROBIAL ACTIVITY
Microbial Off-Characters During Aging
 Lactic
acid bacteria
 Acetic acid bacteria
 Spoilage yeasts
– Film formers
– Residual sugar utilizers
– Survivalists
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
 S-compounds
 Aldehydes
 Vinyl
phenols
 Amino acid derivatives
 Grape compound metabolites
Microbial Off-Tastes
 Sourness
 Bitterness
 Slimy
(okra) finish
Microbial Off-Colors
 Pink
 Orange
Hazes, Films, Precipitates and Sediments
 Result
of microbial biomass/biofilm
 Production of polysaccharides
 Production/modification of tannin-interacting
components
 Visual or gritty
CHEMICAL REACTIONS
Chemical Off-Characters During Aging
 Unmasking
vineyard defect
 Dependent upon microbial end products
 Oxidation-reduction driven
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
 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
 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 TRANSFER
Contaminant Transfer
 From
corks
 From oak
 From winery flora
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
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
 TCA
 MDMP
 Geosmin
 Compounds
made by winery flora (molds
and bacteria) can be absorbed into the
wine
Today’s Program
 Chemical
Issues During Aging
 Spoilage by Acetic Acid Bacteria
 Yeast Spoilage
 Emphasis: Brettanomyces