SURVIVAL OF SACCHAROMYCES CARLBERGENSIS ASSOCIATED TO DIACETYL EVOLUTION DURING WORT FERMENTATION

In the present study, the different steps of brewing were described and yeast population as well as diacetyl production was analyzed during wort fermentation in order to improve the quality of final beer. Steps in the brewing process were composed of malting, milling, mashing, lautering, boiling, fermenting, conditioning, filtering, and packaging. Yeast grew according to a growth curve including a brief lag, exponential, stationary and declined phases. Diacetyl production was observed the eleventh day of fermentation at rate of 0.53 mg/L which decreased to reached 0.14 mg/L at fourteenth day. Young yeasts gave better multiplication and flocculation factors compared to the old one. Our study revealed that the time taken for diacetyl reduction to reach below 0.15 ppm varied from 3 to 4 days depending on yeast generation. This study gave valuable information for better understanding of the fermentation and diacetyl production which can be used to improve beer quality.