Analysis of antioxidants represents a challenge.

With the increased interest in the efficacy and function of natural antioxidants in foods and biological systems, testing for antioxidant activity has received much attention. Although there are many methods we can use to test for antioxidants, there are no approved, standardized techniques.

There is a need to standardize antioxidant testing to minimize the apparent confusion in processes used to evaluate antioxidants, according to scientists at the University of California, Davis. They indicate that more valid guidelines and assay protocols are needed.

The activity of antioxidants in foods and biological systems depends on many factors, including the colloidal properties of the substrates, the conditions and stages of oxidation, and the localization of antioxidants in different phases. When you test natural antioxidants in vitro, it is important to consider the system composition, the type of oxidizable substrate, the mode of accelerating oxidation, the methods that may be used to assess oxidation and how to quantify antioxidant activity.

Several techniques now used and some model systems may not evaluate the true protective effects of antioxidants. Moreover, many factors can confound the data obtained. Such factors include the composition of the test system, the substrate to be protected and the way of inducing oxidation. When testing the antioxidant activity of potential food antioxidants or bioactive compounds, the initial goal may be to develop a model system in which basic chemical principles can be deduced.

But we cannot determine the true impact of antioxidants unless the conditions--the complexity of the system--are as close as possible to the conditions under which protection against autoxidation must occur. You have to have very specific knowledge of the mechanisms of oxidation in order to prevent the formation of free radicals and the onset of oxidative deterioration.

Specific lipid model systems should mimic the target food or physiological systems so that they can be protected as best as possible. There are various sources and types of oxidation, and we should first define the targets of oxidation--lipids, protein or DNA, for example--before selecting techniques for assessing the protective properties of antioxidants under the conditions of their possible use.

Further information. Edwin Frankel, Department of Food Science and Technology, University of California, Davis, CA 95616; phone: [phone]; fax: [phone]; email: [e-mail].