Sodium benzoate
Sodium benzoate (E211), also called benzoate of soda, has chemical formula NaC6H5CO2. It is the sodium salt of benzoic acid and exists in this form when dissolved in water.  It can be produced by reacting sodium hydroxide with benzoic acid.

# Uses
Sodium benzoate is a preservative. It is bacteriostatic and fungistatic under acidic conditions.  it is used most prevalently in acidic foods such as salad dressings (vinegar), carbonated drinks (carbonic acid), jams and fruit juices (citric acid),  pickles (vinegar), and Chinese food sauces (soy, mustard, and duck). It is also found in alcohol-based mouthwash and silver polish. Sodium benzoate is declared on a product label as 'sodium benzoate' or E211. The taste of sodium benzoate cannot be detected by around 25 percent of the population, but for those who can taste the chemical, it tends to be perceived as sweet, sour, salty, or sometimes bitter.
It is also used in fireworks as a fuel in whistle mix, a powder which imparts a whistling noise when compressed into a tube and ignited.
It is found naturally in cranberries, prunes, greengage plums, cinnamon, ripe cloves, and apples. Concentration as a preservative is limited by the FDA in the U.S. to 0.1% by weight though organically-grown cranberries and prunes can conceivably contain levels exceeding this limit.  The International Programme on Chemical Safety found no adverse effects in humans 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.  Sodium benzoate is, however, allowed as an animal food additive at up to 0.1%, according to AFCO's official publication.

# Mechanism of food preservation
The mechanism starts 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%.

# Safety and health
In combination with ascorbic acid (vitamin C, E300), sodium benzoate and potassium benzoate may form benzene, a known carcinogen. Heat, light and shelf life can affect the rate at which benzene is formed.
Professor Peter Piper of the University of Sheffield claims that sodium benzoate by itself can damage and inactivate vital parts of DNA in a cell's mitochondria. "The mitochondria consumes the oxygen to give you energy and if you damage it - as happens in a number of diseased states - then the cell starts to malfunction very seriously. And there is a whole array of diseases that are now being tied to damage to this DNA - Parkinson's and quite a lot of neuro-degenerative diseases, but above all the whole process of aging."

## ADHD
Research published in 2007 for the UK's Food Standards Agency suggests that sodium benzoate (E211) is linked to hyperactive behaviour and decreased intelligence in children.  According to the report, a high consumption of sodium benzoate is associated with a reduction in IQ of close to 5.5 points.    On 6 September 2007, the British Food Standards Agency issued revised advice on certain artificial food additives, including sodium benzoate (E211).
Professor Jim Stevenson from Southampton University, and author of the report, said: "This has been a major study investigating an important area of research. The results suggest that consumption of certain mixtures of artificial food colours and sodium benzoate preservative are associated with increases in hyperactive behaviour in children.
"However, parents should not think that simply taking these additives out of food will prevent hyperactive disorders. We know that many other influences are at work but this at least is one a child can avoid."
Two mixtures of additives were tested in the research:
Mix A:
- Sunset yellow (E110)
- Tartrazine (E102)
- Carmoisine (E122)
- Ponceau 4R (E124)
- Sodium benzoate (E211)
Mix B:
- Sunset yellow (E110)
- Quinoline yellow (E104)
- Carmoisine (E122)
- Allura red (E129)
- Sodium benzoate (E211)
Sodium benzoate was included in both mixes, but the effects observed were not consistent. The Food Standards Agency therefore considers that, if real, the observed increases in hyperactive behaviour were more likely to be linked to one or more of the specific colours tested.
On 10 April 2008, the Foods Standard Agency called for a voluntary removal of the colours (but not sodium benzoate) by 2009. In addition, it recommended that there should be action to phase them out in food and drink in the European Union (EU) over a specified period.