The inhibitory effect of propionic acid on the growth response of Salmonella typhimurium

Abstract

Organic acids have long been used as additives in food as well as feed to reduce microbial populations including Salmonella spp. This study investigated the in vitro growth responses of S. typhimurium isolated from poultry to organic acids such as propionic acid, acetic acid and ethanol. The growth rates of S. typhimurium in tryptic soy broth (TSB) were significantly decreased at concentrations of 0.2 to 2.0% (v/v) buffered propionic acid mixture (BPA) and no growth was observed at 3% (v/v) BPA. The growth rates of S. typhimurium in TSB at various concentrations of ethanol were significantly decreased from 0.3 to 3.0% (v/v) and no growth was observed at 5% (v/v) ethanol. The growth rates of S. typhimurium in minimal media were significantly decreased at concentrations of 0.06% (10 mM) to 0.3% (50 mM) and no growth was observed at 0.6% (100 mM) acetic acid. The effects of various BPA concentrations on the growth rates of S. typhimurium inoculated from the two growth phases of logarithmic phase and stationary phase were determined. In the absence of BPA, the logarithmic phase cells grew faster (P<0.05) than the stationary phase cells. At both 0.6 and 0.8% BPA, the stationary phase cells grew faster (P<0.05) than the logarithmic phase cells. Overall the cells from the stationary phase were more resistant to BPA than those from the logarithmic phase. Consequently, propionic acid can be thought to be a good preservative to reduce S. typhimurium in food or feed.