(492j) Yeast Nutrition and Practical Aspects During Brewing Fermentations

Nutritional aspects of the surrounding media in living organisms are directly involved in the yield of their activity. Industrially, there are many processes carried out by microorganisms where the profile of the final product, considering its properties and production costs, is completely dependent on the nutrients that are available for them. Brewing industry is one of the most competitive beverage industries in the world. The amounts of beer produced by a world spread brand mark and the competitiveness of this market drive consistent research programs in order to improve and make the brewing process more profitable. The main step of the brewing process, where all aromas and compounds that gives the identity to the beer is the fermentation. In large fermenters, yeast cells consume nutrients from the wort and excrete all of those compounds (i.e. ethanol, carbon dioxide...). An important strategy still could be an opportunity for brewers to make the process more profitable consists in using very concentrated wort during the fermentation in the process resulting in a more concentrated beer at the end. The capacity of the same brewery layout can be raised with no changes in the equipment.

In this work, the nutritional aspects of yeast concerning needs and limitations during fermentation of very high gravity (VHG) worts were studied. Considering nutritional aspects of the brewing process, the yeast could be affected before pitching the wort or/and during the fermentations. Using as target yeast, yeast slurry collected from an industrial storage tank (where the yeast is stored between re-pitching, from industrial fermentation to a new one), several nutrients were tested to evaluate the feasibility of the nutritional yeast pre-treatment regarding to an improved fermentation performance during VHG wort fermentations. The yeast was firstly kept in contact with the nutrients in study (one or a combination of many) at the same conditions of temperature and steering as the industrial plant. The yeast was stored in those conditions during different periods followed by lab-scale fermentations with high stressful media, i.e. high gravity wort to evaluate the fermentation performance. Linoleic acid and Tween 80 are nutrients that could be added just few hours before pitching the wort to the yeast storage tanks, inducing a positive effect on the extract consuming and viability of the cropped yeast. The addition of Mg2+, Ca2+, Zn2+, Cu2+, Fe2+ and K+ were also studied as yeast supplements on yeast storage tanks. Another type of nutrients, as ergosterol, biotin, and acetaldehyde were considered as a possibility of improving the fermentation ability of an industrial strain of S. cerevisiae.