Enterobacteriaceae (EB, n = 149), Lactobacillus (LB, n = 162) and Leuconostoc sp. (LC, n = 89) and enterococci (EC, n = 137), isolated from raw meat (n = 65), fermented sausages (n = 50) and cheese (n = 55) samples, were cultivated in a broth containing precursor amino acids (each 3 g/l). After incubation, the liquid culture was chemically analysed for cadaverine (CAD), putrescine (PUT), histamine (HIS) and tyramine (TYR) formation at pH 5.2 and at pH 6.7. The majority of EB isolates (147 of 149) was capable of forming >100 mg/l of either CAD or PUT. Among the most frequently isolated species Hafnia alvei and Serratia liquefaciens, formation of >100 mg/l HIS occurred, but with low prevalence (1.6 and 6.5%, respectively). Twelve of 149 isolates (8%) were able to produce more than 10 mg/l HIS. One hundred forty-two isolates (95.3%) produced less than 10 mg/l TYR, and 7 isolates (4.7%) 10 mg/l to a maximum of 35.3 mg/l TYR. For LB + LC, one isolate (Leuconostoc mesenteroides ssp. mesenteroides) formed >100 mg/l PUT and one >100 mg/l CAD (of all 251 LB + LC isolates 0.4% each). Formation of >100 mg/l HIS and TYR was detected in 3.6 and 19% of the LB + LC isolates, respectively. For the EC isolates, maximum levels for PUT, CAD and HIS were 25.4 mg/l, 6.0 mg/l and 15.7 mg/l, respectively. TYR was formed in quantities of 100–1000 mg/l by 47.9% of EC faecalis (n = 75), and 59.7% of EC faecium (n = 62) isolates. More than 1000 mg/l TYR were formed by 50.7 and 35.5% of the isolates, respectively. A low initial pH of 5.2 compared to the initial pH of 6.7 favoured tyramine production by lactic acid bacteria, but was associated with lower CAD yield by EB.
A considerable intra-species variability in amine formation was observed.
Biogenic amines formation Intra-species variability Raw meat Fermented sausage Cheese