HPLC shows that a number of S. thermophilus isolates produced
biogenic amines in histidine decarboxylase (HDB) (Table 1). All S.
thermophilus isolates had the ability to produce ammonia. Thirtynine
strains of S. thermophilus produced below 100 mg/L of ammonia,
while the other strains produced more than 100 mg/L.