RAPID MATURATION OF BEER USING AN IMMOBILIZED YEAST BIOREACTOR .1. HEAT CONVERSION OF ALPHA-ACETOLACTATE

Methods of heat treating young beer in order to accelerate the beer maturation process were investigated. In conventional beer brewing, the two-step conversion of alpha-acetolactate to diacetyl and of diacetyl to acetoin occurs concurrently and is a time-consuming process, the first step being rate limiting. The optimum conditions for achieving the first step by heat treatment and determination of the heat conversion rate constant are described. Under aerobic conditions, alpha-acetolactate was converted to diacetyl but under anaerobic conditions, it was converted to acetoin. The decay constant of alpha-acetolactate, however, was identical in both conditions. Operating pressure and the effect of heat treatment on beer quality were examined. The heat treatment of young beer under anaerobic conditions is a novel maturation method in that alpha-acetolactate can be converted directly to a flavorless substance (acetoin).