Reducing the Foodborne Pathogens (E.coli 0157:H7 and Staphylococcus aureus) growth in Low Salt condition using soy sauce starter cultures

Abstract

The use of Tetragenococcus halophilus and Zygosaccharomyces rouxii as soy sauce starter culture has been known to produce volatile aromatic and flavor confounding compounds, however none has exposed the microbial safety capability of these starter cultures. In this study, the effect of soy sauce starter inoculation against model pathogenic bacteria, Staphylococcus aureus and Escherichia coli O157:H7 was investigated in an artificial sterile low-salt fermentation condition. The result showed that all samples containing S. aureus had a drop down of pH to a relatively same value (± 4.8) in every type of treatment while E. coli O157:H7 was not able to survive in the low-salt fermentation condition in which the experiment took place. Interestingly, there was no significant reduction in S. aureus colony number for samples treated with T. halophilus (p>0.05) while Z. rouxii treated samples had significant reduction in S. aureus colony number (p<0.05). It was observed that the drop down of S. aureus colony number in samples inoculated with Z. rouxii were followed by a huge drop of reducing sugar to an undetectable level at the end of fermentation period. Furthermore, as the reducing sugar content diminished, the ethanol content inside Z. rouxii treated samples increased.