Acidic alcoholic beverages have a strong microbial killing effect

Abstract

Low-concentration ethanol or weak acids alone have only a weak antimicrobial effect. However, when these are mixed to make acidic ethanol, the antimicrobial power increases synergistically. For example, when a kind of bacteria is suspended in a mixture of HCl (pH 3) and ethanol (10%), their survival rate drops to less than 0.01% compared to treatment with either HCl or ethanol alone. This occurs because ethanol molecules are incorporated into the lipid bilayer of the microbial cell membrane, increasing its permeability. As a result, H+ which are abundant in the external medium flow into the microbial cells, lowering the internal pH. The drop in intracellular pH causes disorder in intracellular molecules and structures, ultimately leading to cell death. Therefore, in the early stage of a meal, alcoholic beverages mixed with acidic gastric juice will kill ingested microbes in the stomach. As the meal progresses, however, gastric acid becomes diluted, causing the microbe-killing effect to be lost. If so, sour alcoholic beverages may kill microbes regardless of the pH in the stomach. Actually, Japanese Ume liqueur (Umeshu), sour white liquor, and wine have a strong bactericidal effect, which may help reduce the risk of food poisoning.