Regulation of Growth and Enterotoxin A Production by Staphylococcus aureus in Cooked Rice and Rice Balls Containing Sodium Chloride and Commercial Seasonings

Abstract

  The purpose of this study was to estimate the effect of sodium chloride (NaCl) on the growth of Staphylococcus aureus and staphylococcal enterotoxin A (SEA) production in cooked rice, and then to find the effective combination of NaCl and commercial seasonings to inhibit the growth and SEA production without impairing the taste of cooked rice. The SEA production was not inhibited in cooked rice containing 0.8–1.5% NaCl, the range usually used to make rice balls, although the production was decreased in that containing 3–7% NaCl. Among about 80 seasonings added to cooked rice containing 1.5% NaCl, 15 seasonings showed inhibitory effect against the growth. The addition of rice vinegar, balsamic vinegar, mustard paste, and rose hip tea prevented the growth of the bacteria and the SEA production although they survived up to 12 h after incubation at 37ºC. We proposed some preparation examples of rice balls containing these seasonings without impairing the taste.