Effect of tyrosine on tyramine formation during beer fermentation

Changes in tyramine, in its precursor amino acid tyrosine, and in Pediococcus spp. were followed during 54 beer fermentations. No statistical relationship between tyramine production and wort tyrosine levels was found, either between the amount of tyramine formed or the decrease in tyrosine through beer fermentation. However, tyramine formation significantly correlated with Pediococcus spp. contamination (r=0.876; P<0.001, n=54). Higher initial tyrosine levels did not induce greater tyramine formation when a similar degree of contamination by Pediococcus spp. occurred, either between tyrosine decrease and tyramine formation. Special attention is required in controlling the presence of lactic acid bacteria to minimise the formation of tyramine. However, the amount of tyrosine does not seem to be a critical factor in the tyramine formation during beer fermentation.