Bacteriological Properties of and Amine-Production Conditions for Tyramine-and Histamine-Producing Bacterial Strains Isolated from Soybean Paste (Miso) Starting Materials

The conditions for production of amines by tyramine- and histamine-producing bacterial strains (T- and H-strains) isolated from soybean paste (miso) starting materials were examined. These strains grew and produced tyramine and histamine under various conditions which may occur during miso fermentation. Namely, tyramine and histamine were produced at pH above 5.1, at salt concentrations of less than 6% and 4%, under either aerobic or anaerobic conditions and at 15-37°C in MRS medium. Both strains consumed possible precursor amino acids of the respective amines. It is assumed that tyramine and histamine were produced by T- and H-strains during the early stages of miso aging and within a short period, when the salt concentration and pH conditions were optimal. Based on their bacteriological properties, the T-strain was identified as Enterococcus faecium and the H-strain was identified as Lactobacillus sp.