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Negative Impacts of Oxygen in Wine

Negative Impacts of Oxygen in Wine. Linda F. Bisson Department of Viticulture and Enology University of California, Davis. When Is It Over-Oxygenation?. Defects associated with excessive oxygen exposure appear Dependent upon wine composition. Issues With Over-Oxygenation. Chemical

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Negative Impacts of Oxygen in Wine

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  1. Negative Impacts of Oxygen in Wine Linda F. Bisson Department of Viticulture and Enology University of California, Davis

  2. When Is It Over-Oxygenation? • Defects associated with excessive oxygen exposure appear • Dependent upon wine composition

  3. Issues With Over-Oxygenation • Chemical • Enzymatic • Microbial

  4. ChemicalIssues • Alcohols become aldehydes • Organic acids become keto acids • Reaction with thiols and loss of • varietal character • Off-Color formation • Extensive loss of color and wine becomes sherry-like

  5. Aldehydes in Wine • Aldehydes • Acetaldehyde from oxidation of Ethanol • Fusel Aldehydes from oxidation of Fusel Alcohols • Benzaldehyde from oxidation of Benzyl Alcohol • Formed chemically from grape/yeast precursors or directly synthesized by microbes • Perception can be enhanced by acetic acid

  6. Acetaldehyde • Low concentrations: apple, unripe apple • Higher concentrations: oxidized apple, nutty, pungent, chemical • Appearance indicates ethanol is being oxidized and wine should be protected from further oxygen exposure

  7. Fusel Aldehydes • Fusel alcohols (oils) are made during amino acid degradation • Fusel alcohols can be reoxidized to aldehydes during aging • Recent experiments suggest fusel aldehydes may be important “impact” compounds in wine

  8. Fusel Aldehydes • Isobutyraldehyde: banana, acrid, pungent • Isovaleraldehyde: nutty, fruity, cocoa, pungent, acrid • 2-Methyl butyraldehyde: aldehydic, berry, cocoa, musty

  9. Benzaldehyde • Characteristic of oxidized wines • Bitter cherry at low concentrations • Chemical taint at higher concentrations • Can be made microbially

  10. Off-Colors • Browning • Pinking • ‘Going Orange’

  11. Enzymatic Issues • Laccase

  12. Microbial Issues • Spoilage Organisms • Acetic Acid Bacteria • Brettanomyces • Staphylococcus • Flor Yeast

  13. Staphylococcuspasteuri • Isolated from MOX wine • Normal grape flora resident • Obligate aerobe – sign of beyond excessive oxygen exposure

  14. Oxygen Treatments of Wine • Need to know the amount of exposure and its consequences and impact on wine, which will vary by the wine • Monitor for signs of excessive oxygen • If push wine to edge of oxygen consumption, will shorten shelf life

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