Chemistry Reference
In-Depth Information
Fig. 12.3 Chemical structure nordihydroguaiaretic acid (NDGA).
stabilization of vegetable oils, potato chips, animal fats (Kraybill et al., 1949;
Magoffin and Bentz, 1949; Sherwin and Luckadoo, 1970). BHA was approved
for food use as an antioxidant in the late 1940s, while BHT and PG were
approved later. BHT was first patented in 1940 as a petroleum oil antioxidant
and was widely used in the gasoline field and later patented for use in animal
fats and dry breakfast cereals in 1947 (Kraybill et al., 1949). TBHQ was
approved for food use in the United States in 1972, with targeted applications
being polyunsaturated oils (Sherwin, 1989). Regulations governing the use of
synthetic antioxidants vary from country to country and depend upon the food
application in question. It has only been in the last ten years that TBHQ has been
authorized for use in Canada, though its use is restricted to the stabilizing of fats,
oil and lard. Recent amendments found in the European Directive 2006/52/EC
have allowed a somewhat broader use of TBHQ in Europe. Because of studies
that link high doses of BHA with cancer of the forestomachs of rats, BHA finds
itself on the California Proposition 65 list of substances known to the State of
California to cause cancer. Readers are encouraged to consult applicable
regulations for each country of interest for more information.
12.4.2 Properties
While BHA and BHT are highly oil soluble and water insoluble, PG is very
slightly soluble in water and only slightly soluble in animal and vegetable oils.
BHA and propyl gallate are quite soluble in propylene glycol, while BHT is
insoluble in this solvent. BHT is slightly less soluble in animal and vegetable
oils than BHA and TBHQ.
BHA in its pure form has a phenolic odor, while BHT and PG have
practically no odor. BHA can develop a slight pink color in the presence of
alkaline metals (Joyner and McIntyre, 1938). BHT forms a yellow color in the
presence of iron in foods. TBHQ does not form a complex with iron or copper.
PG forms purple or violet complexes with iron, and as such, is best used with
metal chelators such as citric acid. TBHQ can interact with free amines to
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