Effect of non-malted barley on low alcohol and nonalcoholic beer production

Introduction. The aim of the present work was to substantiate for production of low and non-alcoholic beer by changing the wort composition by replacing part of the malt with unmalted barley. Materials and methods. Industrial malt and non-malted barley were used. The alcohol fermentation was carried out using free and alginate-chitosan encapsulated top-fermenting yeast strain Saccharomyces cerevisiae S-33. The mashing regime included two pauses - 30 min at 50 degrees C and 60 min at 77 degrees C. The aldehydes were determined according to the bisulfite method, the ester concentration was determined by ester saponification with NaOH. Metabolites were determined after simple sample distillation of the beer. Results and discussion. The wort extract decreased with the increase in the quantity of non-malted barley. In the selected mashing process, the fermentable sugars varied from 3.4 to 4.17% and accounted for about 50% of the laboratory wort extract. Use of 20% barley as adjunct led to a decrease in wort extract by 10% but it did not significantly affect viscosity. A major drawback of the use of non-malted barley is the increase in the laboratory wort filtration time. Filtration time was within 60-75 minutes when the adjunct was up to 20%. It was selected to replace 20% of the malt with unmalted barley. Wort in semi-industrial conditions with the thus selected quantitative malt/barley ratio was produced (8.03% (w/w) extract and fermentable sugar content of 3.7%.). The resulting wort was subjected to alcoholic fermentation at 10 degrees C for 7 days with free and immobilized cells, and for each variant the fermentation kinetics were determined. The process with free cells was relatively slow and in the first 2-3 days up to 0.4% of alcohol was accumulated, which corresponds to a fermentation rate of 11%. Changes occurred in secondary metabolism - increased ester production, normal higher alcohol formation and weak carbonyl compounds synthesis. In the immobilized cells, the fermentation start was also delayed. The actual process started after the 4th day, the fermentation quickly caught up with the free cell fermentation. As a result, more alcohol (about 0.7% w/w) was accumulated in the laboratory beer, thus enabling its classification as low-alcohol beer, and, fewer metabolites accumulated in the beer, which, in combination with the low fermentation temperature, had a negative effect on the taste profile. Conclusions. Technological regimes for production of low alcohol and non-alcoholic beer have been selected on the basis of analysis of wort sugars, as well as on a study of fermentation kinetics at low temperatures with free and immobilized yeast cells.