Sodium benzoate
Sodium benzoate, also known as benzoate of soda, is the sodium salt of benzoic acid, widely used as a food preservative and a pickling agent. It appears as a white crystalline chemical with the formula.
Production
Sodium benzoate is commonly produced by the neutralization of sodium hydroxide with benzoic acid, which is itself produced commercially by partial oxidation of toluene with oxygen.Reactions
Sodium benzoate can be decarboxylated with strong base and heat, yielding benzene:Natural occurrence
Many foods are natural sources of benzoic acid, its salts, and its esters. Fruits and vegetables can be rich sources, particularly berries such as cranberry and bilberry. Other sources include seafood, such as prawns, and dairy products.Uses
As a preservative
Sodium benzoate can act as a food preservative. It is most widely used in acidic foods such as salad dressings, carbonated drinks, jams and fruit juices, pickles, condiments, and frozen yogurt toppings. It is also used as a preservative in medicines and cosmetics. Under these conditions it is converted into benzoic acid, which is bacteriostatic and fungistatic. Benzoic acid is generally not used directly due to its poor water solubility.Concentration as a food preservative is limited by the FDA in the U.S. to 0.1% by weight. Sodium benzoate is also allowed as an animal food additive at up to 0.1%, per the Association of American Feed Control Officials.
Sodium benzoate has been replaced by potassium sorbate in the majority of soft drinks in the United Kingdom.
In the 19th century, sodium benzoate as a food ingredient was investigated by Harvey W. Wiley with his 'Poison Squad' as part of the US Department of Agriculture. This led to the 1906 Pure Food and Drug Act, a key event in the early [history of food regulation in the United States].
In pharmaceuticals
Sodium benzoate is used as a treatment for urea cycle disorders due to its ability to bind amino acids. This leads to excretion of these amino acids and a decrease in ammonia levels. Recent research shows that sodium benzoate may be beneficial as an add-on therapy in schizophrenia. Total Positive and Negative Syndrome Scale scores dropped by 21% compared to placebo.Sodium benzoate, along with phenylbutyrate, is used to treat hyperammonemia.
Sodium benzoate, along with caffeine, is used to treat postdural puncture headache, respiratory depression associated with overdosage of narcotics, and has been used experimentally with ergotamine to treat vascular headache.
Other uses
Sodium benzoate is also used in fireworks as a fuel in whistle mix, a powder that emits a whistling noise when compressed into a tube and ignited.Mechanism of food preservation
The mechanism starts with the absorption of benzoic acid into the cell. If the intracellular pH falls to 5 or lower, the anaerobic fermentation of glucose through phosphofructokinase decreases sharply, which inhibits the growth and survival of microorganisms that cause food spoilage.Health and safety
In the United States, sodium benzoate is designated as generally recognized as safe by the Food and Drug Administration. The International Programme on Chemical Safety found no adverse effects in rats at doses of 647–825 mg/kg of body weight per day.Cats have a significantly lower tolerance against benzoic acid and its salts than rats and mice.
The human body rapidly clears sodium benzoate by combining it with glycine to form hippuric acid which is then excreted. The metabolic pathway for this begins with the conversion of benzoate by butyrate-CoA ligase into an intermediate product, benzoyl-CoA, which is then metabolized by glycine N-acyltransferase into hippuric acid.