Influence of Agitation on the Propagation of Saccharomyces cerevisiae in the Process of Manufacturing Artisan Beers

Abstract

Aims: In view of the growth of the production of artisan beers and the influence of aeration on microbial growth, this work aimed to show the importance of approaching the transfer of oxygen in aerobic fermentation processes. Study Design: In this study the agitation in the propagation of yeast Saccharomyces cerevisiae in the artisan brewing process was carried out, as it is of fundamental importance to consider the function of oxygen in the control of the metabolism and growth of the yeast. Place and Duration of Study: Laboratory of Food Microbiology, University of Uberaba, between June 2016 and July 2016. Methodology: The research was carried out at the Laboratory of Microbiology of Food and for the propagation, a dry malt extract (DME) was used, which is basically obtained by the hydrolysis of the raw and malted barley, and then subjected to concentration, vacuum dehydration and milling. For the fermentation process, the lyophilized yeast of Saccharomyces cerevisiae, Fermentis® brand, safarine strain US-05®, with the initial concentration of 19 x 109 cells per gram, was used in 11.5 g sachets, as indicated by provider. The strain was obtained from a specialist trade and is a neutral American yeast with no ester and high tolerance to alcohol. The wort, with an initial density of 1.035 g.cm-3, was prepared by dissolving 45 g of DME in 450 mL of boiling water and after 15 minutes of boiling it was cooled to 25°C. This procedure was repeated twice by obtaining propagation means 1 and 2. The yeast 11.5 g volume was divided into two portions and each portion was hydrated in 50 mL of distilled water at room temperature and inoculated into the propagation media 1 and 2. Sample 1 was shaken on a Nova Ethics® Kline shaker with rotation set at 120 RPMs for 10 hours. Sample 2 was rested and homogenized for collection every 1 hour for 10 hours. The determination of the cellular concentration (cel/mL) was performed in Neubauer chamber (1/400 mm2 x 1/10 mm) and for the determination of viable and non-viable cells, the International Coloring Method was used, using methylene blue as described in the methodology proposed by ASBC (1996). Viability is given by the ratio of viable cells to total cells. Results: The system that remained with constant agitation has a growth approximately 15% greater than the system without agitation. Conclusion: From the results obtained, it can be concluded that the propagation of yeast cells plays a fundamental role in the production of beers, whether homemade or industrial, because it increases the amount of viable cells, making the fermentation more intense. Agitation accelerates the consumption of substrate and, consequently, cell multiplication, besides increasing cell viability, which is fundamental for fermentation.