How does alcoholic fermentation occur?
Fermentation may start spontaneously due to indigenous yeasts derived from the grape, or picked up from crushing equipment. More commonly, however, the juice or must is inoculated with a yeast strain of known characteristics. Yeasts not only produce alcohol, but also generate the basic bouquet and flavour of wines. Fermentation is an energy-releasing form of metabolism where both the substrate (initial electron donor) and the by-product (final electron acceptor) are organic compounds. The fundamental difference between respiration and fermentation is that the latter does not require the involvement of molecular oxygen. The most common fermentative pathway is by Saccharomyces cerevisiae, alcoholic fermentation. In it, ethanol acts as the final electron acceptor (by-product), while glucose is the preferred electron donor (substrate). Although the primary by-product is ethanol, additional yeast metabolites generate most of the aromatic compounds found in wine. Please note that in wine sci
