In order to study the effects of wort amino acid composition on the changing levels of vicinal diketones (diacetyl and 2,3-pentanedione) during fermentation, samples of fermenting worts supplemented with different amino acids were analysed at intervals by gas chromatography. The activity of acetohydroxy acid synthetase (AHAS), which catalyses the formation of alpha acetolactate (a precursor of diacetyl) was also measured. The amino acids threonine, alanine and glutamate were found to decrease vicinal diketones levels, as did ammonium chloride. These substances, together with valine and leucine, were also found to inhibit AHAS activity. Lysine, on the other hand, had no effect on vicinal diketones or AHAS. The fact that wort amino acid composition can influence vicinal diketone levels may prove useful in the optimization of commercial brewery fermentation processes.
Keywords : amino acid composition diacetyl enzyme fermentation synthesis vicinal diketones wort