THE RESPONSE OFSACCHAROMYCES CEREVISIAETO FERMENTATION UNDER CARBON DIOXIDE PRESSURE

Abstract

When laboratory fermenters containing 4 litres of wort were maintained under a variety of conditions at an excess pressure of 2 atm of carbon dioxide throughout fermentation by Saccharomyces cerevisiae (NCYC 1108), the fermentation rate, yeast growth and final concentration of fusel oils all decreased and the final pH increased. This agrees with reported work on the effect of carbon dioxide pressure on fermentation by S. carlsbergensis. The effect of carbon dioxide pressure on the production and removal of vicinal diketones and their precursors by S. carlsbergensis is known to be variable but except at very low temperatures, pressure has either no effect or increases the rate of removal of these compounds in the final stages of fermentation. In the present experiments with a strain of C. cerevisiae, however, carbon dioxide pressure always led to the fresh beer having a higher lever of vicinal diketones and their precursors than the control fermentation, even at temperatures up to 20°C.