Bactericidal Effects of Coffee and Chlorogenic Acid on Escherichia coli and Salmonella spp. under Low pH or Gastric Acid Conditions

Abstract

The aim of this study was to evaluate the bactericidal effects of coffee and chlorogenic acid (CQA) on Escherichia coli and Salmonella spp. under low pH conditions simulating gastric juice. E. coli and Salmonella sp. survived at pH 1.5 and pH 3.0, respectively, for 3 h at 37 °C in our experimental conditions. However, 1.0% soluble coffee and 0.5% CQA killed E. coli at pH 1.5, and Salmonella spp. at pH 3.0, respectively. Thus, coffee and CQA showed bactericidal activity under low pH conditions. Although CQA showed stronger bactericidal activity than coffee, considering the content of CQA in soluble coffee, the bactericidal effect of soluble coffee could not be only attributed to CQA. The ethyl acetate fraction prepared from soluble coffee showed the highest activity. As this fraction contained various phenolics as well as CQA, these phenolics may be effective in killing the bacteria under low pH conditions.