Effect of Oxygen Supply on Flavor Formation during Continuous Alcohol-Free Beer Production: A Model Study

摘要

The influence of oxygen supply on the formation and conversion of themost important flavor compounds during continuous, alcohol-free beer productionwas studied in a complex model medium. The medium contained inorganicsalts, nutrients, and aldehydes (hexanal, 2-methyl propanal, 3-methylbutanal, and furfural) and mimicked real brewery wort, with the advantageof a constant composition. Fermentation experiments were carried out in acontinuously operating gas-lift reactor, with brewing yeast immobilized onspent grains. The formation (ethanol, higher alcohols, esters, vicinal diketones,and acetaldehyde) and reduction (aldehydes) of flavor-active compoundsat different aeration rates were observed. The results suggest thatthe oxygen supply represents an influential tool for controlling the degreeof fermentation and flavor formation carried out by an immobilized biocatalyst.Under optimal oxygen supply conditions in the continuously operatinggas-lift reactor, it was possible to obtain a fermented model mediumwith a composition approaching that of commercial alcohol-free beers producedby batch process.