Peanut extracts may be natural antioxidants.

Peanut skins and hulls are low-value byproducts of peanut processing operations. We know that natural compounds with antioxidant activity exist in peanut hulls. Natural antioxidants are of great interest to processors because they are better accepted by consumers. Moreover, the safety of synthetic antioxidants has been questioned.

Little effort has been made to extract natural antioxidants from peanut skins and hulls and to test their efficacy in actual food systems. But researchers at Virginia Polytechnic Institute and State University investigated a variety of extraction scenarios to determine which would offer the best way to recover antioxidants from peanuts. They also wanted to test the antioxidant activity of the extracts in model systems. Based on their work, it appears that extracts sourced from peanut processing byproducts may find use as natural antioxidants in foods.

In their research, methanol and ethanol were used to prepare extracts from the skins and hulls of raw peanuts. The scientists tested the extracts for antioxidant potency by adding them to peanut paste and to cooked chicken model systems. Such models provide more accurate predictions of antioxidant activity than simple food systems can offer.

The peanut pastes were spiked with extracts and stored at 40 C for seven to 10 days. Cooked minced chicken was spiked and stored at 8 C for four days. The researchers extracted lipids and determined peroxide values in order to assess oxidation levels. The peanut hull and skin extracts had significant antioxidant activity in the model systems, although there were significant differences in the activity of extracts prepared using methanol and ethanol.

The scientists found that the methanol extracts had slightly more measurable antioxidant activity than methanol. They used methanol to a greater extent because they can obtain completely pure methanol more easily than pure ethanol. Methanol toxicity is not a problem, as methanol is completely removed from the extracts before they are added to the food systems. For added safety, it may be possible to use nontoxic supercritical solvents with or without a co-solvent instead of methanol.

Further information. Sean O'Keefe, Department of Food Science and Technology, Virginia Polytechnic Institute and State University, 119 Food Science and Technology Building, Mail Code 0418, Blacksburg, VA 24061; phone: [phone]; fax: [phone]; email: [e-mail].