Microbial Protease or Yeast Extract—Alternative Additions for Improvement of Fermentation Performance and Quality of Beer Brewed with a High Rice Content

Abstract

Reduction of production costs is an important advantage of adjunct utilization in brewing. Nevertheless, addition of 40% rice significantly decreases the biomass formation of yeast due to depletion of assimilable nitrogen in the wort. This leads to longer fermentation times and may have a negative influence on beer organoleptic quality. This study compared addition of protease to the malt-mash during mashing or supplementation of yeast extract in wort after boiling to increase the wort assimilable nitrogen content. In both cases, the fermentation was considerably accelerated, and the beer quality was significantly improved. Yeast extract gave better results than microbial protease. The fermentation kinetics and the beer quality from a 60% malt-40% rice wort supplemented by yeast extract were the same as those from a 100% malt wort.