Sorbic Acid

Sorbic acid and its potassium salt are the most widely used forms of this compound and are collectively known as sorbates. The salt forms are highly soluble in water, as is true for all organic acids. Their most common use is preservation of food, animal feed, cosmetic, and pharmaceutical products, as well as technical preparations that come in contact with the human body. Methods of application include direct addition into the product; dipping, spraying, or dusting the product; or incorporation into the wrapper (Ranun 1999).

Typical use levels in foods range for 0.02% in wine and dried fruits to 0.3% in some cheeses (Table 1). Food in which sorbate has commercially useful antimicrobial activity

Table 1 Typical concentration (%) of sorbic acid used in various food products

Cheeses

0.2-3.0

Beverages

0.03-0.10

Cakes and pies

0.05-0.10

Dried fruits

0.02-0.05

Margarine

0.05-0.10

Mayonaise

0.10

Fermented vegetables

0.05-0.20

Jams and jellies

0.05

Fish

0.03-0.15

Semimoist pet food

0.1 -0.30

Wine

0.02-0.20

Fruit juice

0.05-0.20

Source: Liewen and Marth (1985).

Source: Liewen and Marth (1985).

include baked goods (cakes and cake mixes, pies and pie fillings, doughnuts, baking mixes, fudges, and icing), dairy products (natural and processed cheese, cottage cheese, and sour cream), fruit product (artificially sweetened confections, dried fruit, fruit drinks, jams, jellies, and wine) vegetable products (olives, pickles, and relishes salads), and other miscellaneous products (certain fish and meat products, mayonnaise, margarine, and salad dressings) (Sofos and Busta 1993).

Environmental factors such as pH, water activity, temperature, atmosphere, type of microbial flora, initial microbial load, and certain food components, singly or in combination can influence the activity of sorbate. Together with preservatives such as sorbic acid, they often act to broaden antimicrobial action or increase it synergistically. Use of other preservatives in combination with sorbate can broaden or intensify antimicrobial action. If growth of spoilage or pathogenic organisms is inhibited, but the microorganism is not killed, growth will eventually resume under proper conditions. The length of inhibition will vary with storage temperatures as well as with any of the other factors discussed.

Sorbic acid is a broad-spectrum antimycotic that is effective against yeast and molds. The antifungal effect of sorbate is greater at pH less than 5.0. Sorbic acid has little antifungal activity at pH values higher that 5.6. Above this pH, little of the acid is in the antimicrobially active dissociated form. However, sorbic acid has a relatively high dissociation constant compared to benzoic or propionic acids and is, therefore, usually the most effective of the organic acids at pH levels of 5.0 or higher. This is presented in Table 2 (Luck and Jager 1997; Ray and Bullerman 1982).

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