Bacteriostatic Lactic acid

Lactic acid may pose as an example inasmuch as it can act either in a bactericidic or bacteriostatic manner, depending on the specific inhibitory conditions. This has been noted specifically for inhibition of L. monocytogenes where lactic acid is able to either kill or limit growth of the organism. Lactic acid is now included in growth prediction models for this pathogen (Gravesen et al., 2004). 

Dubos" concluded that lactic acid has a bacteriostatic effect on Mycobacterium tuberculosis, which increased as pH decreased. Experiments carried out with Bacillus coagulans in tomato paste showed that lactic acid was four times more effective regarding the inhibition of bacterial growth compared to malic, citric, propionic, and acetic acid. ... 

The acidity of food is related to the amount of undissociated and dissociated forms of carboxyKc acids and oxonium ions, respectively, that are present. The major substances that give a sour taste in foods are undissociated hydroxycarboxylic acids, citric and malic acids. Often, however, other carboxylic acids occur, such as ascorbic acid in most types of fruits, tartaric acid in grapes, isocitric acid in blackberries, oxalic acid in rhubarb, lactic acid in some dairy products (such as yoghurt), fermented cucumbers, cabbage, oKves, vinegar and propionic acid in Emmental type cheeses (see Section 8.2.6). The acidity of cola drinks is provided by phosphoric acid, sometimes accompanied by citric or other acids. Carboxylic acids also act as bacteriostatic agents and affect a number of biochemical and chemical reactions. 

Lactic acid (pJC = 3.83 at 25 °C, see Section 8.2.6.1.3) occurs as a natural compound in many fermented products (e.g. yoghurt, fermented sauerkraut and olives). As a preservative, lactic acid (E270) is mainly used as an addulant The undissociated form diffuses through cell membrane of many bacteria and lowers the pH within the cell. It has a bacteriostatic effect on pathogenic bacteria Mycobacterium bovis, a member of the M. tuberculosis bacteria, the causative agent of bovine tuberculosis in cattle. Lactic acid is also effective against other bacteria, so it is used, for example, for surface decontamination of meat and in production of dehcacies. Usually it is applied in combination with sodium lactate. 

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