Page 171 - Natural Antioxidants, Applications in Foods of Animal Origin

150 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir fish products to maintain freshness, prevent rancidity and are particularly

important in food containing large amount of lipids. Therefore, addition of
antioxidants to fish products greatly extends shelf life and maintains flavor
and aroma for as long as possible. The antioxidant activity of a particular
compound, mixture of compounds, or a natural source, is generally related
to its ability to scavenge free radicals, decompose them, or quench singlet
oxygen (Shahidi, 1997).

Antioxidants can be derived naturally as well as chemically synthesized
although their performance levels differ. Both antioxidants function by
donating electron density to fats, thus preventing their breakdown. Gener-
ally, natural antioxidants are known to have higher beneficial health effects
such as their ability to prevent disease, for example, cancer and heart disease
as compared to the synthetic ones(Morton et al., 2000).

4.4.1 SYNTHETIC ANTIOXIDANTS
Synthetic antioxidants do not occur in nature hence, are chemically synthe-
sized to help prevent lipid oxidation in food. The use of synthetic antioxi-
dants dates back to the 1940s when butylated hydroxyanisole (BHA) was
found to retard oxidation and the effectiveness of several alkyl esters of
gallic acid was unraveled. Furthermore, it was also evident that the harmful
effects of transition metals such as iron and copper had to be counteracted;
hence, certain acids, such as citric acid (CA), and their derivatives, were
found to act as metal deactivators in combination with phenolic antioxidants
(Barlow & Hudson, 1990). In 1954, butylated hydroxytoluene (BHT) was
also approved for food use in the United States and tert-butylhydroquinone
(TBHQ) was commercialized in 1972. Synthetic antioxidants are divided
into primary and secondary antioxidants. Primary antioxidants which
prevent the formation of free radicals are further divided into:

• Radical terminators: These constitute the bulk of synthetic antioxi-
dants which prevent lipid oxidation by terminating the free radical
chains. Examples include: BHA, BHT, propyl gallate (PG), TBHQ,
dodecyl gallate (DG), and octyl gallate (OG).
• Oxygen scavengers: These function as reducing agents. Example:
sulphites, ascorbyl palmitate, and glucose oxidase.
• Chelating agents: These prevent lipid oxidation by binding the cata-
lysts such as heavy metals (copper, iron, etc.), either by precipitating