Yeasts Induce Acetaldehyde Production in Wine Micro-oxygenation Treatments

Micro-oxygenation (Mox) is a common technique used to stabilize color and reduce harsh astringency in red wines. Here, we investigate the role of residual sugars, phenolics, SO₂, and yeast on the oxidation of wine in three studies. In a Mox experiment, populations of yeasts emerged after the loss of SO₂, and this was associated with sharp increases in oxygen consumption and acetaldehyde production. No acetaldehyde production was observed without the presence of yeast. In an oxygen saturation experiment, unfiltered wines, in particular those with residual sugar >3 g/L, consumed oxygen more quickly and produced more acetaldehyde than filtered wines. In a final experiment, the reincorporation of oxygen and glucose immediately after the completion of fermentation of an otherwise dry synthetic wine resulted in significant acetaldehyde production. These experiments highlighted the importance of yeast metabolism in determining a wine's response to Mox and suggested that the role of chemical oxidation to produce acetaldehyde during Mox may not be very important. It appears that control of microbial populations and residual sugar levels may be key to managing Mox treatments in winemaking, and production scale experiments should be conducted.