 The key basic principle on the mode of action of organic acids on bacteria is that non-dissociated (non-ionized) organic acids can penetrate the bacteria cell wall and disrupt the normal physiology of certain types of bacteria that we call "pH-sensitive", meaning that they cannot tolerate a wide internal and external pH gradient.Among those bacteria are "Escherichia coli", "Salmonella" spp., "C. perfringens", "Listeria monocytogenes", and "Campylobacter" species.Upon passive diffusion of organic acids into the bacteria, where the pH is near or above neutrality, the acids will dissociate and lower the bacteria internal pH, leading to situations that will impair or stop the growth of bacteria.