Effect of wort plato and fermentation temperature on sugar and nitrogen compound uptake and volatile compound formation.

Takahashi, S., Yoshioka, K., Hashimoto, N. and Kimura, Y.

Abstract
The results of the fermentation process are well known to be influenced both by wort composition and by the conditions prevailing during fermentation, but much remains to be discovered about the precise effects of variations in specific characteristics of the wort or process conditions and about the relationships between the influences of different variables. Laboratory fermentation trials are described in which the wort original gravity varied from 5 to 17 degrees P, the fermentation temperature was either 8 or 14 degrees C and the pitching rate was 6, 8 or 12 g centrifuged yeast per litre. The composition of the sugar, amino acid and volatile compounds contents of the beer produced in each trial was determined. It was found that higher wort gravities led to slower uptake of disaccharides and nitrogenous compounds (especially glycine, tryptophan and tyrosine), decreased production of higher alcohols and increased ester formation, while low temperature decreased the uptake of disaccharides and trisaccharides, and high temperature increased higher alcohol formation. It was also noted that the rate of yeast proliferation, which is known to be linked to amino acid uptake, was (as expected) affected in the same way by variations in original gravity and temperature.
Keywords : amino acid beer brewers' yeast composition ester fermentation fusel alcohol metabolism original gravity sugar synthesis temperature wort