C6H5COOH or C7H6O2, Benzoic Acid, is a crystalline solid that is colorless and it is the most basic type of the aromatic organic acid. The salts of Benzoic Acid are used for preserving food. Benzoic Acid acts as an essential precursor for synthesizing other organic chemical substances.
History of Benzoic Acid
It was in the 1500’s that Benzoic Acid was first discovered. Nostradamus in 1556 described the gum benzoin dry distillation and then by Alexius Pedemontanus in 1560 and later in 1596 by Blaise de Vigenere.
In 1830, Pierre Robiquet & Antoine Boutron Charland were 2 French chemists who wanted to obtain amygdalin from the Prunus dulcis fruit or bitter almonds. They were able to produce benzaldehyde from the bitter almonds but they weren’t able to interpret properly the amygdalin structure. They missed the C7H50 benzoyl radical in the identification. The identification of the benzoyl radical was achieved just a few months later by Friedrich Wohler and Justus von Liebig. They were able to determine the benzoic acid composition. They were then able to investigate the relation between hippuric acid and benzoic acid. Benzoic acid was discovered by Salkowski in 1875 to have antifungal abilities. It was used for the preservation of cloudberry fruits.
Industrial preparation of Benzoic Acid
Partial oxidation of Toluene is the process used to produce the Benzoic Acid commercially. The catalyst used is Cobalt or the Manganese naphthenates. The process is using inexpensive raw materials and produces a large amount of the Benzoic Acid. The process is also environmentally friendly. The production of US is around 126,000 tonnes a year and much of this is being domestically consumed and the remainder is used by industrial chemicals.
Uses of Benzoic Acid
Feedstock
Benzoic Acid is used for many chemicals such as Benzoyl Chloride which is obtained by treating the Benzoic Acid with the Thionyl Chloride or by phosgene, or with one of the chlorides from phosphorus. The Benzoyl Chloride is an essential starting material in producing derivatives of Benzoic acid such as benzyl benzoate that is used as artificial flavouring and also as insect repellant.
Benzoic Acid and salts are being used for preserving food and it is represented with E210 until E213. The Benzoic Acid stops the growth of molds, bacteria and yeast. It can be added directly or can be formed through reaction with calcium, potassium or sodium salt. The benzoic acid is absorbed to the cell initially If the Ph is lower than 5 then the anaerobic fermentation through the phosphofructokinase of glucose will be decreased by 95%. That means that the efficacy of benzoate and benzoic acid depends largely on the food’s pH level. Acidic foods are preserved with benzoates and benzoic acid. Such foods include citric fruit juices, soft drinks, sparkling drinks, and pickles. The amount of the benzoic acid in the foods is just between 0.05 to 0.1%. Other foods that may use a maximum level of the benzoic acid are laid on the international food law. There are concerns that the benzoic and salts can react with ascorbic acid or vitamin C to form benzene.
Medicinal
Whitfield’s Ointment contains Benzoic acid. This ointment is used for treating fungal skin diseases like ringworm, tinea, and athlete’s foot. As the main component of the Benzoin resin, it is also a primary ingredient for the Friar’s Balsam and Tincture of Benzoin. These products had long been used as topical antiseptics as well as inhalant decongestants.
Food Preservative
The Sodium benzoate is 200 times more soluble compared to the benzoic acid. Although benzoic acid is better as an antimicrobial agent, the Sodium benzoate is more preferred. Only 0.1% of the Sodium benzoate is already enough to preserve products that are prepared properly and with a pH adjusted to 4.5 or less. It’s used as preservative for the soft drink industry as well as for the high fructose corn syrup used in carbonated beverages. It’s also being used to preserve sauce, pickles and fruit juices. The Sodium benzoate and Benzoic acid are being used in edible coatings as antimicrobial agents.
Biology and Health Effects
It is found naturally as free Benzoic acid or as a bounded Benzoic Acid esters from different plants and animals. 0.05% can be found in many berries while some Vaccinium fruits such as cranberries contain between 0.03 to 0.13% of the free benzoic acid. Apples that have been infected with the Nectria galligena fungus also have Benzoic acid.
Animals with Benzoic Acids are the male muskoxen, Rock Ptarmigan, and Asian bull elephants and other similar kinds. The gum benzoin has 20% of the free benzoic and 40% of the benzoic acid esters. Hippuric acid contains the Benzoic acid thus it is present in mammals’ urine. Human body can also produce hippuric acid at 0.44 grams per liter a day. But if the person is exposed to benzoic acid or toluene then this amount could increase.
World Health Organization’s Int’l Programm on Chem. Safety or IPCS suggests that humans should not exceed the 5 mg/kg of their body weight a day of benzoic acid. Cats, on the other hand, can tolerate benzoic acid and salts much lower than a rat or mouse. At 300 mg per kg of cat’s body weight will already be lethal. For rats’ oral LDFO is 3040 mg/kg while mice at 1940 to 2263 mg per kg.
In Taipei a health surveyor last year found that 30% of their tested dried or pickled food products failed because of high levels of benzoic acid. This is known to affect the kidney and liver as well as excess cyclamate.
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