USDA Scientists Find Treasure in Peanut Skins

DAWSON, Ga., Dec. 12--Peanut blanching mills sell peanut skins as animal feed for less than a penny a pound. But this red, papery by-product may have a new use in some hair conditioners and cosmetics, a U.S. Department of Agriculture scientist says.

Chemist Richard J. Cole said studies of peanut skin oil have identified a fatty acid--behenic acid--that is often used to give hair conditioners and moisturizers their smoothing properties.

"We found peanut skins had up to 17 percent oil, a potentially valuable extract in itself at 43 cents a pound," said Cole of the USDA's Agricultural Research Service."But we were curious about a waxy substance that settled out at the bottom of our oil samples. When we analyzed it further, we discovered it was long-chain fatty acids, including behenic acid."

Behenic acid currently is extracted from rapeseed flour and sells for about $8 a pound, depending on its purity. It's used mainly in make-up and natural body-building products.

A ton of peanut skins could yield as much as 13 pounds of long-chain saturated fatty acids, mainly behenic and lignoceric. A typical U.S. peanut mill produces about 17 tons of skins per week.

Cole said the behenic and lignoceric acids were discovered when a visiting Russian scientist, Victor Sobolev, tried to create new products from the skins. He and Cole did the studies at ARS' Peanut Research Laboratory in Dawson, Ga.

Sobolev saw the waxy precipitate in the bottom of his oil samples and decided to analyze it using gas chromatography. He is now researching the fatty acids on a two-year assignment at the lab. He said the high levels of behenic and lignoceric acid in the skin oil offer potential commercial uses, but costs such as processing and handling will have to be considered.

Sobolev said one possibility is to see if the combination of fatty acids found in the oil has moisturizing properties beyond those of behenic acid.

Based on standard laboratory extraction procedures, a ton of peanut skins yields up to 160 pounds of oil before roasting. Roasting the skins boosts the oil yield to 340 pounds, but adversely alters the fatty acids, eliminating them as a revenue source.

Scientific contact: Richard J. Cole and Victor Sobolev, Peanut Research Laboratory, Agricultural Research Service, USDA, Dawson, Ga. 31742; phone (912) 995-4441, fax (912) 995-7416, [email protected]; [email protected].