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Value of free radical scavenging tests may be limited.

Lipid oxidation is a major problem in foods. It can cause changes in texture and appearance, create off-flavors, impact a product's aroma and decrease its nutritional quality. The ability of compounds to inhibit lipid oxidation is believed to depend on both their physical and chemical properties.

The most common molecules attacked by oxidation are unsaturated fats. Oxidation causes them to turn rancid. Oxidized lipids are often discolored and usually have unpleasant tastes such as metallic or sulfurous flavors. Even less fatty foods, such as fruits, are sprayed with sulfurous antioxidants prior to air-drying.

There have been numerous attempts to relate the free radical scavenging capacity of a compound to its ability to act as an antioxidant in foods and other biological systems. Scientists at the University of Massachusetts and colleagues elsewhere compared the free radical scavenging activity of various compounds to their ability to inhibit lipid oxidation in oil-in-water emulsions and cooked ground beef. Their data indicate that a compound's free radical scavenging activity does not directly correlate with its ability to inhibit lipid oxidation in the cooked beef and emulsions. This, in turn, suggests that free radical scavenging assays may have limited value in predicting the ability of a compound to act as an antioxidant in complex foods.

The researchers determined the free radical scavenging activity of various polar compounds. They found that the activity of ferulic acid was greater than that of coumaric acid, which was greater than that of propyl gallate. This, in turn, was greater than that of gallic acid,

which was greater than that of ascorbic acid. The researchers also determined the free radical scavenging activity of various non-polar compounds. For these, the activity of rosmarinic acid was greater than that of butylated hydroxytoluene (BHT), which was greater than that of tert-butylhydroquinone (TBHQ), which was greater than that of tocopherol.

Of these compounds only propyl gallate and TBHQ were able to inhibit lipid oxidation in cooked ground beef. Only propyl gallate, TBHQ, gallic acid and rosmarinic acid inhibited lipid oxidation in the oil-in-water emulsions.

Further information. Eric Decker, Department of Food Science, Room 236, Chenoweth Laboratory, University of Massachusetts, 100 Holdsworth Way, Amherst, MA 01003; phone: 413-545-1026; fax: 413-545-1262; email: edecker@foodsci.umass.edu.
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Publication:Emerging Food R&D Report
Date:Apr 1, 2010
Words:369
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