Potassium benzoate

Description

Potassium benzoate is the potassium salt of benzoate. It is mostly used for food preservation for inhibiting the growth of mold, yeast and bacteria since it can create low pH condition after entering into the cells to suppress the anaerobic fermentation of glucose. It can also be used in the whistle in many fireworks. In analytic chemistry, it can be used as eluents for ion chromatography to increase the detector response.

Chemical Properties

Potassium benzoate occurs as a slightly hygroscopic, white, odorless or nearly odorless crystalline powder or granules. Aqueous solutions are slightly alkaline and have a sweetish astringent taste.

Chemical Properties

Potassium benzoate ( E212 ) , the potassium salt of benzoic acid, is a food preservative that inhibits the growth of mold, yeast and some bacteria. It works best in low-pH products, below 4.5, where it exists as benzoic acid.
Acidic foods and beverages such as fruit juice (citric acid), sparkling drinks (carbonic acid), soft drinks (phosphoric acid), and pickles (vinegar) may be preserved with potassium benzoate. It is approved for use in most countries including Canada, the U.S., and the EU, where it is designated by the E number E212. In the EU, it is not recommended for consumption by children.

Uses

Potassium Benzoate is manufactured primarily for food and beverage use. It is a chemical preservative, which in very low concentrations inhibits the activity of the microorganisms. It is used in carbonated beverages. The shelf life of un-pasteurized cider can be greatly extended by adding potassium benzoate. It is also used as the whistle in many fireworks.

Uses

Pharmaceutic aid (preservative).

Production Methods

Potassium benzoate is prepared from the acid–base reaction between benzoic acid and potassium hydroxide.

Flammability and Explosibility

Not classified

Pharmaceutical Applications

Potassium benzoate is predominantly used as an antimicrobial preservative in a wide range of beverages, foods and some pharmaceutical formulations. Preservative efficacy increases with decreasing pH; it is most effective at pH 4.5 or below. However, at low pH undissociated benzoic acid may produce a slight though discernible taste in food products.
Increasingly, potassium benzoate is used as an alternative to sodium benzoate in applications where a low sodium content is desirable.
Therapeutically, potassium benzoate has also been used in the management of hypokalemia.

Safety Profile

Combustible when exposed to heat or flame. When heated to decomposition it emits acrid smoke and irritating fumes.

Safety

Potassium benzoate is widely used in food products and is generally regarded as a nontoxic and nonirritant material. However, people with a history of allergies may show allergic reactions when exposed to potassium benzoate. Ingestion is inadvisable for asthmatics. Higher concentrations of potassium benzoate have been reported to cause irritation to mucous membranes.
The WHO acceptable daily intake of total benzoates including potassium benzoate, calculated as benzoic acid, has been estimated at up to 5 mg/kg of body-weight.

Safety

Potassium benzoate was recently described by the Food Commission, who campaign for 'safer, healthier food in the UK', as "mildly irritant to the skin, eyes and mucous membranes".
Cats have a significantly lower tolerance to benzoic acid and its salts than rats and mice.

Synthesis

One very common way to make potassium benzoate is by oxidizing toluene.
Another way to synthesize potassium benzoate in the lab setting is by reacting methyl benzoate with potassium thio acetate.

storage

Potassium benzoate is stable at room temperature under normal storage conditions. Since it is slightly hygroscopic, potassium benzoate should be stored in sealed containers. Exposure to conditions of high humidity and elevated temperatures should be avoided.

Purification Methods

Potassium benzoate [582-25-2] M 160.2. Crystallise it from water (1mL/g) between 100o and 0o. [Beilstein 9 III 375, 9 IV 279.]

Spectra

Carbon 13 NMR
The carbon NMR shows 5 unique peaks. There are four peaks between 130 - 140 ppm from the carbons in the benzene ring. There is an additional carbon peak around 178 ppm representing the carbon from the carbonyl.
Infrared spectrum The following are the main peaks in the IR spectrum.
1610: C=O from carbonyl
1580: C=C from benzene ring.

Mechanism of food preservation

The mechanism of food preservation begins with the absorption of benzoic acid into the cell. If the intracellular pH changes to 5 or lower, the anaerobic fermentation of glucose through phosphofructokinase is decreased by 95 %.

Incompatibilities

Potassium benzoate is incompatible with strong acids and strong oxidizing agents.

Regulatory Status

GRAS listed. Accepted as a food additive in Europe. Included in the Canadian List of Acceptable Non-medicinal Ingredients.

References

Gjerde, Douglas T., and J. S. Fritz. "Sodium and potassium benzoate and benzoic acid as eluents for ion chromatography." Analytical Chemistry 53.14(1981):2324-2327.
Zengin, N., et al. "The evaluation of the genotoxicity of two food preservatives: Sodium benzoate and potassium benzoate." Food & Chemical Toxicology An International Journal Published for the British Industrial Biological Research Association 49.4(2011):763-9.
Zeb, Alam, et al. "Grape juice preservation with benzoate and sorbate. " Advances in Food Sciences (2009).
Marietta, Michael S. "Fireworks artillery shell." US, US6912958. 2005.

Raw materials

Preparation Products