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Food Lipids: Chemistry, Nutrition, and Biotechnology

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would be imprudent to discount any of these theories as to the nature <strong>and</strong> activity<br />

of antioxidant MRPs.<br />

7. Phospholipids<br />

The antioxidative action of phospholipids is not well understood. It is likely that<br />

antioxidant activity differs among the various phospholipids as a result of the wide<br />

variance in functional groups <strong>and</strong> structures. Possible actions include regeneration<br />

of primary antioxidants, metal chelation, <strong>and</strong> decomposition of hydroperoxides.<br />

Phospholipids have been shown to be synergists. Moreover, phosphatidylcholine<br />

(PC), phosphatidylethanolamine (PE), <strong>and</strong> phosphatidylserine (PS), display antioxidant<br />

activity that is possibly linked to chelating ability [47]. Lecithin, once an important<br />

commercial antioxidant, now sees limited use because of inefficiency as an<br />

antioxidant <strong>and</strong> poor heat stability. Burkow et al. [48] found lecithin to have antioxidant<br />

activity in cod liver oil.<br />

8. Sterols<br />

Sterols have been documented to have antioxidant activity. It is thought that sterols<br />

interact with oil surfaces <strong>and</strong> inhibit oxidation. Sterols may be oxidized at oil surfaces<br />

<strong>and</strong> inhibit propagation by acting as hydrogen donors. Maestroduran <strong>and</strong> Borjapadilla<br />

[49] have reviewed sterol antioxidants <strong>and</strong> provided information about recent patents.<br />

9. Sulfur Dioxide <strong>and</strong> Other Sulfites<br />

Sulfites are reducing agents that are weak antioxidants in foods. Sulfites such as<br />

sulfur dioxide, sodium sulfite, <strong>and</strong> sodium, potassium, <strong>and</strong> metabisulfites are used to<br />

prevent flavor <strong>and</strong> color degradation in beverages <strong>and</strong> fruits. Sulfites react with molecular<br />

oxygen to form sulfates. They also act as reducing agents that promote the<br />

formation of phenols from quinones, thereby preventing browning reactions.<br />

10. Gums<br />

Polysaccharides have been studied for their antioxidant effects. Gums are primarily<br />

used for their texture-enhancing effects, but they also possess antioxidant activity,<br />

which may be due to metal chelation <strong>and</strong> oxygen consumption, <strong>and</strong> their viscosityincreasing<br />

effects [50,51]. Guaiaconic acids present in the resin of the Gaujacum<br />

officinale L. tree are responsible for the antioxidant activity of this food additive<br />

[15]. Guaiac gum was commonly used to preserve refined animal fats but has limited<br />

use now. It is not as potent as synthetic antioxidants, has poor heat stability, <strong>and</strong> is<br />

fairly expensive. Xanthan gum, pectin, guar gum, <strong>and</strong> tragacanth gum are recognized<br />

as antioxidants.<br />

11. Antioxidants in Plants<br />

Antioxidant components of plants include vitamin E homologs, carotenoids, proteins,<br />

<strong>and</strong> many other compounds. Plants produce a diverse assortment of phenolic metabolites<br />

that readily undergo oxidation <strong>and</strong> have the potential to minimize effects of<br />

autoxidation. Several phenolics in addition to vitamin E (Sec. III.B.1) have shown<br />

potential for use as food antioxidants or are already serving as such. Common plant<br />

phenolic antioxidants include gallic acid (as a constituent of polymeric gallotannins<br />

<strong>and</strong> ellagitannins) <strong>and</strong> protocatechuic acids, phenylpropanoids, <strong>and</strong> mixed-pathway<br />

metabolites such as alkyl ferulates, flavonoids, <strong>and</strong> suberins [52]. Gallic acid is typ-<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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