Antimicrobial activity of acetic acid is related to pH, and the undissociated form of the acid is primarily responsible for antimicrobial activity. When this ester is dissolved in solution, undissociated acetic acid can penetrate the cell membrane lipid bilayer of bacteria and yeasts and release protons into the cytoplasm because the cell interior has a higher pH than the exterior (Booth, 1985; Davidson, 2001; Marquis, Clock, & Mota-Meira, 2003).