Influence of Aeration and Suspended Material on Higher Alcohols, Acetoin, and Diacetyl during Fermentation

Abstract

The formation of higher alcohols or fusel oil during the fermentation of grape musts was greatly increased under vigorously aerobic conditions compared to anaerobic fermenations. In one free-run must the increase was sevenfold, but it was usually about double the amounts formed under anaerobic conditions. Naturally occurring suspended solids also stimulate higher alcohol formation. Isobutyl and isoamyl alcohols accounted for most of the increase resulting from either aerobic conditions or the presence of suspended matter for which the amounts of <i>n</i>-propyl and active amyl alcohols were little changed. Both grape skins and inert solids stimulated higher alcohol formation. Evidence was obtained to indicate that the influence of suspended solids was attributable to adsorbed oxygen. Very high levels of acetoin and diacetyl were formed under aerobic conditions, and significant amounts of these compounds were found in some submerged culture "flor" sherries.