Yeast vitality and beer quality

The relationship between yeast vitality and beer quality has been studied t hrough fermentation and storage tests on a pilot scale. The yeast vitality was determined precisely by measuring the intracellular pH value. Clear flu ctuations in yeast vitality were seen to the dependent an the storage tempe rature of the yeast. The critical value in this case was a storage temperat ure of 4 degrees C. Moreover, the relationship between yeast vitality and b eer quality was studied. Corresponding with the yeast vitality there were c lear differences in the fermentation speed and FAN consumption. The brighte ning of the wort with fermentation and the concentration of the vicinal dik etone of the beer were influenced in such cases by the vitality of the yeas t used for fermentation. The beer froth was poorer and also the concentrati on of medium chain fatty acids and the protease activity of the beer increa sed when less vital yeast was used.