Isolation and selection of native yeast potentially usable in craft brewery

Abstract

Craft beer in Argentina is an innovative sector that promotes regional productive poles. Craft production of beers gains relevance when reaches regional identity through the incorporation of local products to elaboration. The yeast is critical to beer, which involves much more than converting sugars into alcohol, it contributes to beers flavors and aroma too. With the aim to generate a technological transfer to craft breweries, we have developed an isolation and selection procedure of native yeast from grape and evaluated its potential use in beer production. The yeasts were isolated from the grape bloom. Three (3) isolates (C1, C2, and C3) strains, which were identified as Saccharomyces cerevisiae by biochemical tests (API 20 C BioMérieux), were selected for the study. The yeasts were inoculated in beer wort and cultivated at 20°C. In final products, there were evaluated alcohol production, transparency/turbidity, and organoleptic characteristics by sensory analysis. Commercial yeast was used as a control. The three evaluate strains show a product color similar to commercial yeast (amber yellow). But the strain named C3 showed better ability of alcohol production, with values of 3.73% alcoholic graduation, similar to control yeast (4.18%). The strains C1 and C2 showed very low values of 0.64 and 0.59%, respectively. Regarding transparency/turbidity, the strain C3 was presented limpid with low turbidity (like control), while the C1 and C2 strains showed high turbidity. Finally, the sensory analysis indicated that only C3 showed a pleasant aromatic profile and excellent taste in the mouth, with acceptable acidity. These preliminary results indicate that the C3 strain could be successfully used in craft brewery, due to its similarities to commercial yeast. Future studies are needed to adjust fermentation temperatures, batch volume, reproducibility over time, number of cells and viability necessary and conservation conditions.