Sesame Seed Oil Extract May Improve Soy Oil for Frying

By Marcia Wood
December 19, 2013

Fried foods that you can order at restaurants, delis or other eateries all across America may have been prepared with soybean oil. In fact, soy oil makes up an estimated 70 to 80 percent of all cooking oil used commercially in the United States.

Now, U.S. Department of Agriculture (USDA) scientists are determining how to better protect soy oil's good-for-you polyunsaturated fats from the oxidation that can occur at the high temperatures typically used for frying.

Oxidation can make the oil heavy and gummy, can lead to off-flavors and odors, and can cause the oil to form a messy foam during deep-frying, according to Agricultural Research Service (ARS) research chemist Hong-Sik Hwang, who heads the soy oil studies. ARS is USDA's chief intramural scientific research agency.

The combined effects of oxidation may shorten the usable life of the oil, which, in some commercial settings, is reused until health regulations or quality problems dictate discarding it.

Hwang and ARS research chemists Erica L. Bakota, Mark A. Berhow, Jill K. Winkler-Moser, and research leader Sean X. Liu are investigating interesting natural antioxidant compounds that might effectively and affordably protect soybean oil from oxidation during frying.

In preliminary experiments at the ARS National Center for Agricultural Utilization Research in Peoria, Ill., the scientists found that sesamol, extracted from sesame seed oil, provided better antioxidant protection for soy oil than nine other natural antioxidants that the team tested.

Importantly, the team's tests with french fries showed that sesamol, when added to soy oil at the rate of 6,600 parts per million, provided better protection than TBHQ, a synthetic antioxidant, added at the allowable maximum of 200 parts per million.

In describing the research for an article in the November-December 2013 issue of Agricultural Research magazine, Hwang noted that TBHQ is commonly added to soy cooking oil that's sold in bulk for commercial use.

Hwang cautions that even though sesamol is a natural, edible compound, more research is needed to ensure that using it at levels that provide antioxidant protection for the soybean oil would, at the same time, meet federal GRAS (Generally Recognized As Safe) standards.

The idea of pairing a sesame seed compound with soybean oil to thwart oxidation isn't new. But the Peoria group is apparently the first to investigate the concept using deep-frying tests that simulate commercial conditions.

Peer-reviewed articles published this year and in 2012 in the Journal of the American Oil Chemists' Society document this ARS research.