Effect of Coreopsis tinctoria microcapsules on tyramine production by Enterococcus faecium in smoked horsemeat sausage

This work investigated the inhibitory effects of Coreopsis tinctorius essential oil (CTEO) and Coreopsis tinctorius microcapsules (CTM) on tyramine accumulation by Enterococcus faecium in pure culture and during the ripening of smoked horsemeat sausage, in order to provide a novel natural additive for the control of tyramine in smoked horsemeat sausage. To evaluate the expression of related-genes in the tyrosine decarboxylation (TDC) pathway, we used reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to determine the expression of tyrosine decarboxylase (tyrDC) and tyrosine/tyramine antiporter (tyrP) genes. Furthermore, the pH, moisture content, microorganisms and tyramine accumulation of sausage were assessed. The results revealed that CTEO and CTM markedly ( P ＜ 0.05) decreased tyramine accumulation by inhibiting E. faecium growth and the expression of tyrDC and tyrP genes. Furthermore, tyramine accumulation in sausage was evidently inhibited by CTEO and CTM, and the inhibitory effect of CTM was more significant ( P ＜0.05). Hence, CTM addition is a desirable approach to inhibit tyramine accumulation, and enhance the safety of smoked horsemeat sausages.