Butylated Hydroxyanisole and Butylated Hydroxytoluene
Butylated Hydroxyanisole and Butylated Hydroxytoluene
Butylated hydroxyanisole (BYOO-til-ay-ted hi-DROK-see-ANN-i-sole) and butylated hydroxytoluene (BYOO-til-ay-ted hi-DROK-see-TOL-yoo-een) are very popular food additives used to preserve fats and oils. They both are antioxidants, which are compounds that prevent oxygen from reacting with substances and changing them into other materials. BHA and BHT prevent the oxidation of fats and oils that would convert them into rancid, foul-smelling, harmful products.
BHA is a white or pale yellow waxy solid with a faint pleasant odor. BHT is a white crystalline solid. Both compounds are members of the phenol family of organic compounds. The phenols are compounds containing a benzene ring of six carbon atoms to which is attached at least one hydroxyl (-OH) group.
BHA and BHT
BHA: C11H16O2; BHT: C15H24O
Carbon, hydrogen, oxygen
BHA: 180.24 g/mol; BHT: 220.35 g/mol
BHA: 51°C (124°F); BHT: 71°C (160°F)
BHA: 268°C (514°F); BHT: 265°C (509°F)
Both are insoluble in water and soluble in ethyl alcohol; BHT is also soluble in acetone and benzene
HOW IT IS MADE
A variety of methods are available for the preparation of BHA. The most common method involves the reaction between p-methoxyphenol (CH3CH2OC6H4OH) and isobutene ((CH3)2C=CH2) or tert,-butyl alcohol ((CH3)3COH) over a catalyst of silica (silicon dioxide; SiO2) or alumina (aluminum oxide; Al2O3) at temperatures of about 150°C (302°F). BHT is usually made by reacting p-cresol (CH3C6H4OH) with isobutene.
COMMON USES AND POTENTIAL HAZARDS
The most important use of both BHA and BHT is as food preservatives. When these compounds are added to products containing fats or oils, oxygen reacts with the additive (BHA or BHT) rather than the food itself, protecting the food from spoiling. Among the vast array of food products containing either BHA or BHT or both are cereals, seasonings, frostings, dessert mixes, instant potatoes, packaged popcorn, baked goods, pie crusts, meat products, potato chips, candy, sausage, freeze-dried meats, butter, cheese, crackers, bread, vegetable oils, margarine, nuts, beer, and chewing gum.
Both compounds are also added to animal feed as preservatives. BHA and BHT are added to a number of non-food products as well. These products include paraffin wax, lipstick, eye shadow, lip-gloss, mascara, body and face lotions, diaper rash ointment, deodorant soaps, moisturizers, and shaving gels and creams.
The antioxidant properties of BHA and BHT make them suitable for other applications also. For example, they are sometimes added to paints and inks to prevent a "skin" from forming on top of these liquids. The skin is formed when the paint or ink reacts with oxygen in air to form a solid compound. The compounds are also used as additives for the preservation of drugs, rubber products, petroleum products, the plastics used in food wraps, and the petroleum wax coatings used on food boxes.
Questions have been raised about the possible health benefits and risks posed by BHA and BHT. On the one hand, these compounds may contribute to good health by destroying substances in the body that can lead to cancer. They may also destroy the herpes virus and the human immunodeficiency virus (HIV). Most nutritionists agree that antioxidants can be helpful in protecting cells and tissues from aging and damage by oxygen.
On the other hand, BHA and BHT may also be responsible for certain health problems. For example, some people appear to be allergic to these compounds, causing skin rashes, hives, or tightness in the chest, although such reactions are thought to be rare. Other people may have problems metabolizing BHA and BHT properly, resulting in a build-up of the compounds in their bodies.
Scientists are uncertain about the possible long-term health effects of BHA and BHT. Some studies suggest that these compounds may affect liver or kidney function or may be carcinogenic. Studies on this subject are inconclusive, however, and the U.S. Food and Drug Administration has decided that the two compounds can be used as food additives if the amount added is less than 0.02 percent by weight.
As with all chemicals, direct exposure to large doses of BHA or BHT can cause serious health problems. In one experiment, for example, adults who ingested four grams (0.14 ounce) of BHA experienced stomach pain, vomiting, dizziness, confusion, and temporary loss of consciousness. That amount of BHA is tens or hundreds of thousands of times the amount one would consume in foods or other products, however. Only people who work directly with the compound would ever worry about an effect such as this one.
Words to Know
- A chemical that causes cancer in humans or other animals.
FOR FURTHER INFORMATION
"Butylated Hydroxyanisole." CHEC's HealtheHouse. http://www.checnet.org/healthehouse/chemicals/chemicalsdetail2.asp?Main_ID=330 (accessed on January 9, 2006).
"Butylated Hydroxyanisole." Gale Encyclopedia of Science. Edited by K. Lee Lerner and Brenda Wilmoth Lerner. 3rd ed., vol. 1. Detroit: Gale, 2004.
"Butylated Hydroxyanisole." Hazardous Substances Data Bank. http://toxnet.nlm.nih.gov/ (accessed on Jnauary 9, 2006).
"Butylated Hydroxyanisole (BHA; tert-butyl-4-hydroxyanisole) and Butylated Hydroxytoluene (BHT; 2,6-di-tert-butyl-p-cresol)." In Food Antioxidants: Technological, Toxicological, and Health Perspectives, edited by D. L. Madhavi, S. S. Deshpande, and D. K. Salunkhe. New York: Dekker, 1996.
"Butylated Hydroxytoluene." Gale Encyclopedia of Science. Edited by K. Lee Lerner and Brenda Wilmoth Lerner. 3rd ed., vol. 1. Detroit: Gale, 2004.
"Butylated Hydroxytoluene." International Chemical Safety Cards. http://www.cdc.gov/niosh/ipcsneng/neng0841.html (accessed on January 9, 2006).