Seleção de leveduras não convencionais e não comerciais para produção de cervejas por fermentação pura, mista e sequenciada com Saccharomyces cerevisea

Abstract

Yeasts of several genera and species are capable of converting sugars to ethanol and carbon dioxide, as well as other minor metabolites, a chemical process known as alcoholic fermentation. In the past, spontaneous fermentation was practiced and characterized by non-Saccharomyces yeasts during the early stages of fermentation, while yeasts of the genus Saccharomyces dominated the later stages. Today, the inoculation of pure yeast cultures provides better process control, however, limiting the complexity of flavor and aroma generated by different strains and species. Given the above, this article aims to carry out an exploratory study of the fermentative kinetics of unconventional yeasts in beer production, whether in simple, mixed or sequenced fermentation, together with a commercial yeast Saccharomyces cerevisiae. To evaluate the fermentation behavior and its effectiveness, the alcohol production, substrate consumption, pH, cell growth and viability of microorganisms throughout the process were analyzed. The study indicated that the unconventional yeasts in pure fermentation showed lower yield when compared to commercial strains of S. cerevisiae, considering the fermentative parameters, with real attenuation varying between 8.84% and 17.79%. In the stage of mixed fermentation between unconventional yeasts and S. cerevisiae, no significant differences were observed in relation to simple fermentation (S. cerevisiae), considering the fermentation parameters. In the step of sequential fermentation, with 48 hours of difference between inoculations, there was a decrease in the yield of the process, with significant differences in relation to the control (S. cerevisiae) for the main fermentation parameters. Considering that most of the unconventional yeast strains showed biomass growth and good adaptability to the fermentation medium, L. thermotolerans and W. anomalus showed promise for the production of low-alcohol beers. In mixed and sequenced fermentation, further studies are needed to verify possible impacts on the sensory characteristics of beers.