Potassium benzoate
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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 United States and the European Union, where it is designated by the E number E212.
Potassium benzoate is also used in whistle compositions in pyrotechnics.<ref>Template:Cite web</ref>
Synthesis
One very common way to make potassium benzoate is by oxidizing toluene to benzoic acid followed by a neutralization with potassium hydroxide:<ref>Template:Cite patent</ref>
Another way to synthesize potassium benzoate in the lab setting is by hydrolyzing methyl benzoate with potassium hydroxide:
Reactions
Potassium benzoate, like sodium benzoate, can be decarboxylated with a strong base and heat:
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%.Template:Cn
Safety and health
Potassium benzoate has low acute toxicity upon oral and dermal exposure.<ref>Template:Cite web</ref> It is a mild irritant to the skin, and has the potential to cause serious eye damage.<ref name="SigmaSDS" />