Methology for reuising yeast in a craft brewery

Abstract

Beer is one of the most widely consumed alcoholic beverages in the world, which reaches all social status and is an industrial sector that generates millions of dollars a year The craft breweries are in Argentina an innovative industrial sector that has experienced a explosive growth in the last fifteen years, particularly high in the San Luis Province (Argentina).. The growing demand for quality craft beers has driven significant technological development, process optimization and cost reduction by the breweries. The yeast is critical to beer, that involves much more than converting sugars into alcohol, it contribute to flavor and aroma to beer too. The reusing of the yeasts is a wanted process that is being by brewers, as it generates significant savings in the production of new batches of beer. This reusing imply the collection of the yeast after the fermentation process from the bottom of the fermentation tank. The handling and collection of healthy yeast, avoiding biological contamination, is a crucial to achieving a good beer quality. With the aim to generate a technological transfer to the craft breweries, we developed a procedure of handling and collection of yeast for reuse in breweries. The work was carried out in the Kerze brewery, located at San Luis Province. Yeast samples were daily taken from the bottom of fermentation tank during all the fermentation process (7 days). In the yeast samples viability was measured using standard methodogy. The results indicated that the time optimal to the yeasts collection for reuse is from 3 to 5 days of fermentation, when the total number of yeast cell is higher (1.43 x109) and the best viability is recorded (90%). After the collection the yeast were stored 24 hours in a refrigerator at 4°C and its viability measured, showing a viability minor than 50%. The results indicate that for yeast reusing, it must be harvested the fifth day of fermentation and reuse for a new batch within 24 hours and stored at 4°C. The implementation of this operative procedure for yeast collection generates an optimal process for resusing beer yeast (quantity of cells and viability necessary) and avoiding losses to craft breweries. Future studies are need in order to increase the storage time of recovered yeast.