Food additives reducing volatility of antioxidants at frying temperature

Authors: Hwang, Hong-Sik; Moser, Jill

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2014
Publication Date: 9/29/2014
Citation: Hwang, H.-S., Winkler-Moser, J.K. 2014. Food additives reducing volatility of antioxidants at frying temperature. Journal of the American Oil Chemists' Society. 91(10):1745-1761.

Interpretive Summary: Vegetable oils, including soybean oil, have nutritional benefits due to the high content of polyunsaturated fats, however these oils are more prone to oxidation which lowers their length of use. Therefore, the food industry avoids using these healthy oils in favor of unhealthy oils containing highly saturated fats. Less oxidation may be achieved by improving the antioxidant activity; one way to do this would be to reduce volatility of the antioxidant at frying temperature. This study identified 22 additives, based on their molecular structures, and found that these additives effectively reduced volatility of the antioxidant. This allowed increased antioxidant activity and prolonged the lifetime of soybean oil at frying temperature. It is believed that this approach could have potential for many antioxidants, synthetic and natural, when volatility is a problem. This new technology would encourage the food industry to use vegetable oils as frying oil. In addition, the prolonged lifetime of frying oil would reduce the amount of waste oil, which counts about 22 billion pounds per year.

Technical Abstract: At frying temperature, antioxidants are lost not only by reaction with radicals formed by oil oxidation, but also by decomposition and evaporation before they are able to exert antioxidant activity. In this study it was hypothesized that an additive that can bind or interact with an antioxidant could reduce volatility of the antioxidant at frying temperature. Three synthetic antioxidants, tert-butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), which have relatively high volatility, were used as antioxidants in this study to examine the hypothesis. Thermogravimetric analysis (TGA) experiments showed that all twenty-two additives tested in this study effectively reduced volatility of the antioxidants. An NMR study showed that signals of BHT shifted by addition of an additive, evidencing the interaction between the two substances in the chloroform solution. To examine the effect of these interactions on antioxidant activity, heating tests were conducted with soybean oil (SBO) containing 200 ppm antioxidants at 180 °C. Oxidation was monitored with 1H NMR for loss of olefinic protons and bisallylic protons in SBO and with gel permeation chromatography (GPC) for polymerized triacylglycerols (PTAG). Improved antioxidant activity of the antioxidants were observed when combined with several additives tested in this study and HPLC analysis showed that the antioxidants were effectively reserved by the additives in SBO during the heating process. The concentrations of the antioxidants retained in SBO were relatively well correlated with the antioxidant activity.