Acetic acid is a natural metabolite in human metabolism and because it has been used in food preservation for thousands of years, it is not classified as a food preservative in EU Directive.
|Structure of acetic acid|
Vinegar normally is used as a preservative in pickling relishes and other foods that have been heated.
As little as 0.1% of the undissociated acid will inhibit the growth of most food poisoning and spore-forming bacteria and 0.3% will prevent the growth of mycotoxigenic moulds.
In vinegar preserves the effect of the acetic acid is frequently enhanced by the presence of salt.