Sorbic acid antimicrobial Properties

Potassium sorbate has both antimicrobial and antifungal properties in formulations below pH 6. Generally, it is used at concentrations of 0.1% to 0.2% in oral formulations (solutions, syrup, and suspensions), and is used much more than sorbic acid because of its higher solubility and stability in water. However, some loss of antimicrobial activity occurs in the presence of nonionic surfactants and some plastics. 

Antimicrobial activity potassium sorbate is predominantly used as an antifungal preservative although it also has antibacterial properties. Similarly to sorbic acid, the antimicrobial activity is dependent on the degree of dissociation there is practically no antibacterial activity above pH 6. Preservative efficacy is increased with increasing temperature, and increasing concentration of potassium sorbate. The efficacy of potassium sorbate is also increased when used in combination with other antimicrobial preservatives or glycols since synergistic effects occur. Reported minimum inhibitory concentrations (MICs) at the pH values indicated are shown in Table... 

Sorbic acid is an antimicrobial preservative with antibacterial and antifungal properties used in pharmaceuticals, foods, enteral preparations, and cosmetics. Generally, it is used at concentrations of 0.05-0.2% in oral and topical pharmaceutical formulations, especially those containing nonionic surfactants. Sorbic acid is also used with proteins, enzymes, gelatin, and vegetable gums. It has been shown to be an effective preservative for promethazine hydrochloride solutions in a concentration of 1 g/L. ... 

Occasionally, confusion arises regarding the applicability and expectations surrounding the use of sterilants and preservatives. Properly administered in correct amounts, a sterilant can be expected to kill 100% of the viable cell population regardless of species. Preservatives, on the other hand, may cause cell death, but, in general, function to inhibit specific populations of microorganisms. Thus, the use of preservative such as SO2 and sorbic and benzoic acids should not be expected to be a carte blanche remedy for control of microorganisms present in the wine at bottling. Other distinctions between the two classes of compounds may also be drawn. The antimicrobial properties of compounds like sorbic acid and sulfur dioxide resides in the undissociated, rather than the ionized, molecule. Thus, inhibitory activity is enhanced at lower pH (Zoecklein et al., 1995). A sterilant, such as DMDC, does not rely on pH for enhanced/diminished activity. 

Sorbic acid, which can be used to increase the antimicrobial properties of sulfur dioxide, is now well known and authorized in many countries. The possibility of using octanoic and decanoic acids will also be covered, though they are not currently authorized. They do not seem to pose any hygiene problems, and they exist... 

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