Survival of biogenic amine-producing dairy LAB strains at pasteurisation conditions

P>Biogenic amines (BAs) are low molecular weight organic bases with biological activity, synthesised by the microbial decarboxylation of precursor amino acids such as histidine, tyrosine or arginine. The consumption of food and beverages containing large amounts of BA can have toxicological effects. This paper reports the resistance of aminogenic lactic acid bacteria strains to pasteurisation (63 degrees C for 30 min). Skimmed milk inoculated with histamine- and tyramine-producing strains of Enterococcus and Lactobacillus was subjected to pasteurisation. The viable number of Enterococcus durans IPLA 655 was reduced by 1 log, while that of Enterococcus faecalis BA64 was reduced by 3 logs. Lactobacillus brevis CECT 3810 did not survive pasteurisation, while the other Lactobacillus strains examined were more resistant; their viable numbers were reduced by about 2 logs. The two most resistant strains, E. durans IPLA 655 and Lactobacillus curvatus VI6, were subjected to higher temperatures. Enterococcus durans was completely inactivated at 78 degrees C, while some live cells of Lb. curvatus were observed. These results show that some native, metabolically active BA producers could be found in pasteurised milk owing to their resistance to the thermal treatment; their presence could have a negative impact on the final content of BAs in dairy products made from such milk.