Low temperature brewing using cells immobilized on brewer’s spent grains

A biocatalyst, prepared by immobilization of the psychrotolerant yeast strain Saccharomyces cerevisiae AXAZ-1 on delignified brewer’s spent grains, was used for brewing at very low temperatures, resulting in beers with fine clarity, excellent quality and mature character after the end of primary fermentation. Fermentation times were low (only 20 days at 0 °C), while ethanol and beer productivities were high, showing suitability of the biocatalyst for very low temperature brewing. Diacetyl (61–167 ppb), 2,3-pentadione (32–109 ppb) and DMS (11–37 ppb) concentrations in all the green beers were low (the lowest values being those found in beers produced at 0–5 °C). GC/GC–MS analysis showed significant quantitative differences in the composition of aroma volatiles, revealing an impact of fermentation temperature on organoleptic qualities. The increased productivities and fine quality of the products, with low vicinal diketone, DMS and amyl alcohol concentrations, may allow elimination of maturation time, resulting in reduction of production and investment costs.