Investigations of the effects of activated carbon and pressure on fusel alcohol formation in wine fermentations

Concentrations of fusel oils (higher molecular weight alcohols) produced by yeast during fermentation were shown to be affected by carbon dioxide partial pressures. When activated carbon, used to eliminate certain colors and flavors in base wines after fermentation, was added prior to fermentation, the quantity of fusel alcohols produced during fermentation increased by as much as 30-35%. Different carbon types and different strains of Saccharomyces cerevisiae, ion exchange resins, and metal addition experiments were performed to confirm that the increase in fusel alcohols is due to the reduction of carbon dioxide partial pressure. The activated carbon appears to be acting as a physical decarbonating agent, eliminating CO{dollar}sb2{dollar} which could be inhibiting the decarboxylase step of the Ehrlich mechanism of fusel alcohol formation. The reverse reaction, to reduce fusel alcohol formation by increasing the carbon dioxide partial pressure, was shown to be successful, with fusel alcohol reductions of up to 45% at 45 psi. Increased partial pressure of CO{dollar}sb2{dollar} reduces fusel alcohol formation, while decreased CO{dollar}sb2{dollar} pressure increases fusel alcohol formation.