Chemistry Reference
In-Depth Information
Fig. 12.4 Chemical Structures of BHT, 3-BHA and 2-BHA, PG and TBHQ.
produce a red colored material (Sherwin, 1989). Commercial BHA contains a
higher proportion of the 3-isomer (90%) than the 2-isomer (see Fig. 12.4).
BHA, BHT, PG and TBHQ are all hydroxy substituted phenols (see Fig.
12.4), and as such, act as radical scavengers by donating hydrogen atoms,
thereby forming more stable phenoxy radicals that do not contribute to the lipid
oxidation mechanism. They can react further to form color bodies, but they do
not otherwise further destabilize the lipid system.
BHT is not as effective as BHA, in general, due to the presence of the two t-
butyl groups, which offer greater steric hindrance. BHT is also more volatile
than BHA and is more readily lost in baking and frying applications. The
antioxidant activity of BHA has been found to increase up to 0.02% and remains
constant after that (Thompson and Sherwin, 1966). BHT, on the other hand, does
not appear to plateau in this manner.
BHA has been shown to have antimicrobial (Chang and Branen, 1975),
antifungal (Ahmad and Branen, 1981), and antibacterial properties (Shelef and
Liang, 1982). TBHQ also has antimicrobial properties (Nanditha and
Prabhasankar, 2009).
12.4.3 Food applications
Oils play an important role in our food systems and have been the basis for many
studies involving oxidation. More is known about the oxidative mechanism of
lipids than is known about the oxidation food components such as proteins and
carbohydrates. Synthetic antioxidants have been used to stabilize many different
types of lipidic systems. They have been effective in vegetable oils, fish oils,
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