Handbook of Enology: Volume 1. Pascal Ribéreau-Gayon

Handbook of Enology: Volume 1 - Pascal Ribéreau-Gayon


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(V5) following deletion of different gene coding for isoforms of acetaldehyde dehydrogenase (Blondin et al., 2002).

Initialsugar (g/l) Fermentedsugar (g/l) Secondary products
Aceticacid (g/l) Glycerol(g/l) Succinicacid (g/l)
224 211 0.26 4.77 0.26
268 226 0.45 5.33 0.25
318 211 0.62 5.70 0.26
324 179 0.84 5.95 0.26
348 152 1.12 7.09 0.28
Graph depicts the correlation between volatile acidity production and the maximum cell population in high-sugar botrytized musts. Schematic illustration of effect of the yeast-assimilable nitrogen content in must (with or without ammonium supplements) on the production of volatile acidity. Schematic illustration of effect of an alcohol-induced precipitate of a botrytized grape must on glycerol and acetic acid formation during the alcoholic fermentation of healthy grape must.

      Other winemaking factors favor the production of acetic acid by S. cerevisiae: anaerobic conditions, very low pH (<3.1) or very high pH (>4), certain amino acid or vitamin deficiencies in the must, and excessively high temperature (25–30°C) during the yeast growth phase. In red winemaking, temperature is the most important factor, especially when the must has a high sugar concentration. In hot climates, the grapes should be cooled when filling the tanks. The temperature should not exceed 20°C at the beginning of fermentation. The same procedure should be followed during thermovinification immediately following the heating of the grapes.

Schematic illustration of effect of the lipid fraction of grape solids on acetic acid production by yeasts during alcoholic fermentation.

      During the alcoholic fermentation of red or slightly clarified white wines, yeasts do not continuously produce acetic acid. The yeast metabolizes a large portion of the acetic acid secreted in must during the fermentation of the first 50–100 g of sugar. It can also assimilate acetic acid added to must at the beginning of alcoholic fermentation. The assimilation mechanisms are not yet clear. Acetic acid appears to be reduced to acetaldehyde, which favors alcoholic fermentation to the detriment of glyceropyruvic fermentation. In fact, the addition of acetic acid to a must lowers glycerol production but increases the formation of acetoin and 2,3‐butanediol. Yeasts seem to use the acetic acid formed at the beginning of alcoholic fermentation (or added to must) via acetyl‐CoA


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