Butylated hydroxytoluene (BHT), also known as dibutylhydroxytoluene, is a lipophilic organic compound, chemically a derivative of phenol, that is useful for its antioxidant properties. European and U.S. regulations allow small amounts to be used as a food additive. In addition to this use, BHT is widely used to prevent oxidation in fluids (e.g. fuel, oil) and other materials where free radicals must be controlled.
|Preferred IUPAC name
Additin RC 7110
3D model (JSmol)
|E number||E321 (antioxidants, ...)|
CompTox Dashboard (EPA)
|Molar mass||220.356 g·mol−1|
|Appearance||White to yellow powder|
|Melting point||70 °C (158 °F; 343 K)|
|Boiling point||265 °C (509 °F; 538 K)|
|1.1 mg/L (20 °C)|
|Vapor pressure||0.01 mmHg (20°C)|
|Safety data sheet||External MSDS|
|GHS Signal word||Warning|
|P273, P391, P501|
|NFPA 704 (fire diamond)|
|Flash point||127 °C (261 °F; 400 K)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|> 2,000 mg/kg (dermal, rat)|
|NIOSH (US health exposure limits):|
|TWA 10 mg/m3|
IDLH (Immediate danger)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Phytoplankton, including the green algae Botryococcus braunii, as well as three different cyanobacteria (Cylindrospermopsis raciborskii, Microcystis aeruginosa and Oscillatoria sp.) are capable of producing BHT. The fruit lychee also produces BHT in its pericarp. Confirmation was made via gas chromatography–mass spectrometry analysis.
- CH3(C6H4)OH + 2 CH2=C(CH3)2 → ((CH3)3C)2CH3C6H2OH
The species behaves as a synthetic analog of vitamin E, primarily acting as a terminating agent that suppresses autoxidation, a process whereby unsaturated (usually) organic compounds are attacked by atmospheric oxygen. BHT stops this autocatalytic reaction by converting peroxy radicals to hydroperoxides. It effects this function by donating a hydrogen atom:
- RO2• + ArOH → ROOH + ArO•
- RO2• + ArO• → nonradical products
BHT is listed under several categories in catalogues and databases, such as food additive, household product ingredient, industrial additive, personal care product/cosmetic ingredient, pesticide ingredient, plastic/rubber ingredient and medical/veterinary/research.
BHT is primarily used as an antioxidant food additive. In the United States, it is classified as generally recognized as safe (GRAS) based on a National Cancer Institute study from 1979 in rats and mice. It is approved for use in the U.S. by the Food and Drug Administration: For example, 21 CFR § 137.350(a)(4) allows BHT up to 0.0033% by weight in "enriched rice", while 9 CFR § 381.147(f)(1) allows up to 0.01% in poultry "by fat content". It is permitted in the European Union under E321.
BHT is used as a preservative ingredient in some foods. With this usage BHT maintains freshness or prevents spoilage; it may be used to decrease the rate at which the texture, color, or flavor of food changes.
Since the 1970s, BHT has been steadily replaced with butylated hydroxyanisole (BHA). Some food companies have voluntarily eliminated BHT from their products or have announced that they were going to phase it out.
BHT is also used as an antioxidant in products such as metalworking fluids, cosmetics, pharmaceuticals, rubber, electrical transformer oil (at 0.35%), and embalming fluid. In the petroleum industry, where BHT is known as the fuel additive AO-29, it is used in hydraulic fluids, turbine and gear oils, and jet fuels. BHT is also used to prevent peroxide formation in diethyl ether and other laboratory chemicals. It is added to certain monomers as a polymerisation inhibitor to facilitate their safe storage. Some additive products contain BHT as their primary ingredient, while others contain the chemical merely as a component of their formulation, sometimes alongside butylated hydroxyanisole (BHA).
The US Food and Drug Administration classifies BHT as generally recognized as safe (GRAS) as a food preservative when used according to approved uses. There is, however, some debate surrounding a possible link between BHT and cancer risk, asthma, and behavioral issues in children; some studies show a potential to increase risk and some to decrease risk. Because of this uncertainty, the consumer group Center for Science in the Public Interest recommend to avoid BHT and puts BHT in its "caution" column. The National Cancer Institute determined in 1979 that it was noncarcinogenic in a mouse model. BHT has low acute toxicity, as do other closely related phenol antioxidants. For example, the LD50 of 2,6-di-tert-butylphenol is greater than 9 g/kg.
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Types of Ingredients: Preservatives[.] What They Do: Prevent food spoilage from [...]; maintain freshness[.] Examples of Uses: Fruit sauces and jellies, beverages, baked goods, cured meats, oils and margarines, cereals, dressings, snack foods, fruits and vegetables[.] Names Found on Product Labels: Ascorbic acid, citric acid, sodium benzoate, calcium propionate, sodium erythorbate, sodium nitrite, calcium sorbate, potassium sorbate, BHA, BHT, EDTA, tocopherols (Vitamin E)[.]
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