Abstract: This study aimed to prepare an inclusion complex ferulic acid (FA) with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and evaluate its effects on the pH, growth, gene expression, and tyramine accumulation in the cultured broth of Enterobacter cloacae L63 and tyramine accumulation in smoked horsemeat sausage inoculated with this strain. Real time-quantitative polymerase chain reaction (qPCR) was used to measure the expression of the tyrosine decarboxylase (tdcA), tyrosine/tyramine antiporter (tyrP), tyrosine t-RNA synthetases (tyrS) and Na+/H+ antiporter (nhaC) genes in the tyramine-producing pathway. In addition, high performance liquid chromatography (HPLC) was employed to detect tyramine accumulation during 48 h of culture of Enterobacter cloacae L63. The results showed that FA and its inclusion complex with HP-β-CD reduced the expression of tdcA and tyrP (P < 0.05), had a strong antibacterial activity against E. cloacae L63, inhibited the increase in the pH of the cultured broth and smoked horsemeat sausage and reduced tyramine accumulation. The inclusion complex was more effective against tyramine accumulation (P < 0.05).

Key words: 2-hydroxypropyl-β-cyclodextrin/ferulic acid inclusion complexes; gene expression; Enterobacter cloacae; high performance liquid chromatography