SUPPRESSION OF α-ACETOLACTATE FORMATION IN BREWING WITH IMMOBILIZED YEAST

Abstract

Immobilized yeast cells extensively produced the diacetyl precursor, α‐acetolactate, during alcohol fermentation. The activity of acetohydroxy acid synthetase, which is responsible for the formation of α‐acetolactate from pyruvic acid, was high in cell‐free extracts of immobilized yeast cells compared with that of free yeast cells. It was suggested that the expression of AHA synthase of immobilized yeast cells was increased during growth in the carrier as compared with free yeast cells. When the initial immobilizing yeast cell concentration was changed from 1.0 × 10⁶ cells/ml to 1.0 × 10⁹ cells/ml, production of α‐acetolactate was reduced from 0.94 mg/l to 0.30 mg/l. Furthermore, during continuous fermentation for 10 d, the concentration of α‐acetolactate in beer was 0.30 mg/l.