What Is Sorbic Acid?
Sorbic acid is a type of organic acid that has antibacterial properties against a wide range of microorganisms.
It is found in the unripe fruit of the Ranunculus Japonicus plant. sorbic acid itself is a crystalline powder that is difficult to dissolve in water. It is therefore used in its high water-soluble potassium salt form, i.e., primarily as potassium sorbic acid.
The main use of sorbic acid is as a preservative added to foods. However, the antimicrobial activity of sorbic acid varies greatly depending on pH; it is more potent at lower pH, i.e., more acidic.
Sorbic acid is a low-carbon fatty acid, and like other fatty acids, it is metabolized and broken down by the body. Therefore, it has a relatively small effect on the body and is not considered as being dangerous.
Uses of Sorbic Acid
Sorbic acid is mainly used as a food additive for preservation. Sorbic acid may also be used in cosmetics as a preservative. It has bacteriostatic action against aerobic bacteria as well as molds and yeasts.
Foods to which sorbic acid may be added and the amounts in which it may be added are specified in the certain codes. Examples of such foods include cheese, dried seafood products, soy sauce pickles, and koji pickles. Each food also has its own standard value for use, i.e., an upper limit for the amount of sorbic acid contained in the food.
Therefore, when manufacturing foods with added sorbic acid, care must be taken not to exceed the upper limit for the amount of sorbic acid contained in the food. Since a standard value has also been established for the allowable daily intake, caution should be exercised when consuming large quantities of food products containing sorbic acid.
The following are examples of foods to which the addition of sorbic acid is permitted:
- Amazake
- Anko (red bean paste)
- Sea urchin
- Fruit wine
- Miso (soybean paste)
- Seafood dry products
- Jams
- Meat products
- Margarine
Characteristics of Sorbic Acid
Sorbic acid is characterized by the fact that its water solubility varies considerably depending on whether it is a salt or not. Since sorbic acid itself is insoluble in water, it must be dissolved before it can be used in food products, and in most cases, it is used in the form of potassium sorbate.
However, even when potassium sorbic acid is added to foods, its antimicrobial activity can be fully demonstrated in acidic conditions, but is slightly reduced in alkaline conditions. When the -COOH of sorbic acid becomes -COOK (potassium salt), its water solubility increases, but its antimicrobial activity decreases.
When the food to which sorbic acid is added becomes alkaline, it tends to become salt like -COOK, and its antimicrobial activity tends to decrease. On the other hand, when the food becomes acidic, sorbic acid may precipitate in the food because it is hard to dissolve in water, although it becomes -COOH and its antimicrobial property increases.
Therefore, care must be taken to control the pH of foods containing sorbic acid. In order to fully demonstrate the preservative effect of sorbic acid, it is necessary to maintain the acidic state by using a pH adjuster.
Structure of Sorbic Acid
The structure (molecular structure) of sorbic acid is that of a 6-carbon unsaturated fatty acid with two unsaturated bonds in the hydrocarbon portion. The molecular formula for sorbic acid is CH3CH=CHCH=CHCOOH. Another name for sorbic acid is 2,4-hexadienoic acid.
Sorbic acid is an acid because it has a carboxylic acid moiety (-COOH) in its molecule. It has a molecular structure similar to that of acetic acid (CH3COOH), which has two carbons. Because it has more carbons than acetic acid, it is less soluble in water, so it is often used as a potassium salt to make it more water soluble.
Other Information on Sorbic Acid
1. Calcium Sorbate
As mentioned above, sorbic acid itself is difficult to dissolve in water, so it is sometimes difficult to use it in foods. Potassium Sorbic Acid, on the other hand, is easily soluble in water and can be used in foods, but requires pH control. Because of these problems, calcium sorbate, which is more soluble in water than sorbic acid, was later approved as a food additive.
2. Advantages of Using Sorbic Acid
Foods to which trace amounts of sorbic acid are added become less susceptible to spoilage. The advantage of the antiseptic effect of sorbic acid is greater than the disadvantage of harming one’s health by eating spoiled food. This point should be taken into consideration when making good use of sorbic acid.