Application of Sorbic acid

Sorbic acid (2,4-hexadienoic acid) is a straight chain unsaturated fatty acid with a molecular weight of 112.13 and the formula: CH3 - CH = CH - CH = CH - COOH. Sorbic acid is commercially produced as a powder or granules, it has a characteristic acrid odor and acid taste. The carboxyl (COOH) group in sorbic acid is very reactive and can form salts with calcium, sodium, and potassium. The potassium salt of sorbic acid is commercially available as a powder or granules. Its molecular weight is 150.22 and it is very soluble in water.
           

Potassium sorbate is used in the production of sweet white table wines. Although BATF permits its use in wine, up to 300 ppm, it is important to remember that its taste threshold is well below the legal limit. The taste threshold for experienced tasters has been reported to be about 130 ppm. Addition of sorbic acid often results in the formation of ethyl sorbate, which is said to impart an unpleasant odor when present in a significant level.

Sorbic acid(CAS.NO:110-44-1) also inhibits mold growth. Some of the important species that are suppressed by sorbic acid belong to the genera Alternaria, Botrytis ,  Cladosporiwn,  Fusariwn , Mucor, Penicilliwn, Rhizopus, Trichoderma. Mold can be a problem in wine cellars. To control mold in the wine cellar, sorbic acid could be included in the antimicrobial compounds used for sanitizing.
Several microorganisms can metabolize sorbic acid particularly when it is present in small concentrations. For this reason, it is not a suitable preservative in foods with high microbial counts. To derive the maximum benefit from the antimicrobial action of sorbic acid, it is important to clean the wine well and keep the microbial count low in the bottled wine. It should be emphasized that sorbic acid inhibits yeast and mold, but not acetic and lactic acid bacteria. In fact, lactic acid bacteria can metabolize sorbic acid and produce off flavored compounds.

The antimicrobial action of sorbic acid is due to its inhibitory influence on various enzymes in the microbial cell. The enzymes inhibited by sorbic acid include the following:

1. Enzymes involved in carbohydrate metabolism such as enolase and lactate dehydrogenase.

2. Enzymes of citric acid cycles such as malate dehydrogenase, isocitrate dehydrogenase, ketoglutarate dehydrogenase, succinate dehydrogenase, and fumerase.

3. Several enzymes containing SH group, and other enzymes such as catalase and peroxidase.

The key points in sorbic acid use are summarized below.

1. Potassium sorbate (most soluble form of sorbic acid) should be used. However, this can cause bitartrate precipition problems.

2. The solubility of potassium sorbate is influenced by temperature, therefore, it should not be added to a cold wine.

3. Wine should be mixed well after sorbate addition.

4. Sorbate should be used in conjunction with sulfur dioxide.

5. Certain yeast and bacteria are not inhibited by sorbic acid.

6. Properly clarified wine (low yeast count), low pH, and relatively high alcohol would help in reducing the amount of sorbic acid needed for effectively controlling yeast.

7. Sorbic acid addition should never be considered as a substitute for poor sanitation. Calculating Potassium Sorbate Additions Sorbic acid is added to a wine in the form of the potassium salt. Potassium sorbate contains 73.97% sorbic acid. In order to calculate the amount of potassium sorbate, the following formula should be used.