THE CONCENTRATION AND SIGNIFICANCE OF PYRUVATE IN BEER

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Abstract
Excretion of pyruvate takes place during the yeast-growth phase of fermentation, and, in batch fermentation, the extent of its accumulation varies directly with the extent of growth. Pyruvate excretion is not related to the content of pyruvate decarboxylase in the cells and is not influenced by the addition of thiamine or alanine to the wort; the pH of the wort exerts a slight influence on pyruvate excretion. Pyruvate may be metabolized by yeast towards the end of fermentation and during conditioning, so that the quantity present in beer is influenced by the extent and timing of yeast separation. The addition of sodium pyruvate to beer alters beer flavour by affecting the ‘mouth feel’ aspect of flavour; the minimum quantity required to do this varies in different beers over a range of 50–400 mg/litre.