Biogenic Amine Changes Related to Lactic Acid Bacteria During Brewing.

Biogenic amine contents and microbial contamination (wild yeasts and lactic acid bacteria) were followed during beer fermentation in both industrial and pilot plants. No significant change in the amine contents was observed, except for tryptamine and tyramine. Tyramine formation showed a great variability (from 8 to almost 30 mg/l), while tryptamine formation was always much lower than tyramine (<3.5 mg/l). No relationship was found between wild yeast counts and tyramine formation, whereas a significant positive relationship was found between tyramine formation and lactic acid bacteria. Colony-forming units (CFU) of these microorganisms ranging from 4 × 10 to 1 × 10 CFU/ml were related to low tyramine production (<5 mg/l). Tyramine formation between 5 and 15 mg/l was related to lactic acid bacteria counts from 1 × 10 to 1 × 10 CFU/ml, while lactic acid bacteria higher than 1 × 10 CFU/ml were related to tyramine formation between 15 and 25 mg/l. No marked tyramine production occurred when lactic acid bacteria counts were lower than 4 × 10 CFU/ml. The lactic acid bacteria isolated were identified as species of Pediococcus . Secondary fermentation was not related to tyramine formation. Phosphoric acid washing of the brewer's yeast was effective in eliminating Pediococcus spp. and, therefore, in reducing tyramine levels in the final product.