Volatile by-products formed in low-temperature wine-making using immobilized yeast cells

The formation of acetaldehyde, ethyl acetate, propanol-1, isobutanol, amyl alcohols and methanol in repeated batch and continuous fermentations of must using a cryotolerant and alcohol-resistant yeast immobilized on delignified cellulosic material (DCM) and gluten pellets was studied. The fine and fruity aroma of the wines prepared may be attributed to the high content of ethyl acetate in the total volatiles. Immobilization of yeast cells increased ethyl acetate production and, in the case of the DCM, decreased amyl alcohol production at low temperatures compared with free cells. With the DCM-supported biocatalyst, the percentage ethyl acetate of total volatiles minus methanol remained constant as the temperature was reduced, while the amyl alcohol content was reduced. Amyl alcohols are thought to be correlated with improvement of the aroma and the decrease in toxicity of the wine. (C) 1997 Elsevier Science Ltd.