The effect of temperature during the fermentation process on American Pale Ale beers

Fermentation process stands out as one of the most important stages in the production of beer, as it involves the metabolization of compounds present in the wort by yeasts, resulting in the formation of ethanol, CO2 and secondary quality compounds, where the production of which substance is influenced by parameters such as fermentation temperature. The aim of this study was to evaluate the temperature for optimizing the fermentation process (15°C, 18°C and 22°C) of four different commercial yeast strains (BRY-97, M-15, US-05 and S-04) of the S. cerevisiae type in the production of physicochemical compounds and quality in beers of the APA type, assessing their productivity. Physicochemical analyses were carried out (soluble solids, pH, density, color and titratable acidity), high-performance liquid chromatography-HPLC, which made it possible to quantify and visualize the metabolic evolution of the yeasts in terms of sugar consumption (maltose, glucose and fructose), production of alcohols and by-products (ethanol, glycerol and xylitol) and their production rate. The physicochemical analyses showed that most of the beers had characteristics within those indicated by current legislation (º Brix 3.5-4.0; pH 4.62 - 4.94; Acidity 10.5-19.5; FG 1.004-1.008; EBC 20.95-28.16). In the chromatographic analyses, the beers did not show significant variations in the values of glucose (0.01 g. L-1), fructose (0.3 g.L-1) and maltose (0.04 g.L-1). In terms of ethanol concentration, yeasts BRY-97 (ABV 4.1 %) and S-04 (ABV 4.4 %) produced more alcoholic beers at all fermentation temperatures. All the yeasts performed very well in the metabolic process, differing from each other only in the speed of conversion of the compounds, but strain M-15 showed the best productivity (1.52 g.(L.h)-1) - 18°C; 1.52 (g.(L.h)-1) of ethanol. In view of the results, it was possible to observe that each yeast strain has particularities and specific characteristics that influence the final fermentation product.