Antimicrobial effects of wine: separating the role of polyphenols, pH, ethanol, and other wine components

While the antimicrobial effectiveness of wine is well documented, relative contributions of the wine components to its antimicrobial activity is controversial. To separate the role of wine phenolics, ethanol, and pH from other wine constituents, the antimicrobial effects of intact wine were compared to that of phenols-stripped wine, dealcoholized wine, ethanol, and low pH applied separately and in combination, against 2 common foodborne pathogens, Salmonella enterica serovar Enteritidis and Escherichia coli. All samples were biochemically characterized with respect to their total phenolics and resveratrol content, antioxidant capacity, ethanol content, and pH. Antioxidative activity of the samples corresponded to their total phenolics content. Except for respective controls, pH and ethanol content were similar in all samples. The order of antibacterial activity of the samples was: intact wine > phenols-stripped wine > dealcoholized wine > combination of ethanol and low pH > low pH > ethanol. Separate application of ethanol or low pH showed negligible antibacterial activity while their combination showed synergistic effect. Antibacterial activity of the samples could not be related to their total phenolics and resveratrol content, antioxidant capacity, ethanol content, or pH. Our study indicates that antimicrobial activity of complex solutions such as intact wine cannot be exclusively attributed to its phenolic or nonphenolic constituents, nor can the antimicrobial activity of wine be predicted on the basis of its particular components.