Tyramine-producing enterococci are equally detected on tyramine production medium, by quantification of tyramine by HPLC, or by tdc gene-targeted PCR

The presence of biogenic amines (BAs) in foods is not acceptable as the consumption of food and beverages containing high levels of BAs could result in toxicological effects for human health. BAs are mainly produced by the microbial decarboxylation of certain amino acids. Among the various BAs, tyramine is the most commonly cited and abundant BA produced by several bacterial genera. Various biochemical, chromatographic and molecular methods are used for the detection of BAs. Among different lactic acid bacteria, enterococci have been found to be the most abundant tyramine producers. In the present study, 28 previously isolated bacteriocinogenic strains of Enterococcus sp. were tested for their ability to produce tyramine by qualitative, quantitative and molecular methods. Correlations between these methods were also investigated. A total of 19 enterococcal strains were found to produce tyramine by all the methods used. A low level of correlation was found between the results of two different decarboxylating media used. Improved medium detected more tyrosine-positive colonies than tyrosine production medium. However, a 100% correlation was observed between the results observed with tyrosine production medium, tdc gene-targeted polymerase chain reaction and tyramine quantification by high performance liquid chromatography. Therefore, these methods may be used to complement each other in the detection of tyramine-producing enterococci in foods.