| Summary: | The study evaluated the role of <i>Enterococcus faecium</i> in tyramine production and its response to fermentation temperature in a traditional Korean fermented soybean paste, <i>Cheonggukjang</i>. Tyramine content was detected in retail <i>Cheonggukjang</i> products at high concentrations exceeding the recommended limit up to a factor of 14. All retail <i>Cheonggukjang</i> products contained <i>Enterococcus</i> spp. at concentrations of at least 6 Log CFU/g. Upon isolation of <i>Enterococcus</i> strains, approximately 93% (157 strains) produced tyramine at over 100 µg/mL. The strains that produced the highest concentrations of tyramine (301.14–315.29 μg/mL) were identified as <i>E</i>. <i>faecium</i> through 16S rRNA sequencing. The results indicate that <i>E. faecium</i> is one of the major contributing factors to high tyramine content in <i>Cheonggukjang</i>. During fermentation, tyramine content in <i>Cheonggukjang</i> groups co-inoculated with <i>E. faecium</i> strains was highest at 45 °C, followed by 37 °C and 25 °C. The tyramine content of most <i>Cheonggukjang</i> groups continually increased as fermentation progressed, except groups fermented at 25 °C. At 45 °C, the tyramine content occasionally exceeded the recommended limit within 3 days of fermentation. The results suggest that lowering fermentation temperature and shortening duration may reduce the tyramine content of <i>Cheonggukjang</i>, thereby reducing the safety risks that may arise when consuming food with high tyramine concentrations.
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