Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2006
Publication Date: 4/30/2006
Citation: Winkler, J.K., Warner, K.A., Glynn, M.T. 2006. Effect of deep-fat frying on phytosterol and polymerized triacylglycerol content in oils with differing fatty acid composition [abstract]. 97th Annual Meeting and Expo of the American Oil Chemists' Society. p. 89. Interpretive Summary:
Technical Abstract: Phytosterols are ubiquitous in plants and are the dominant class of unsaponifiables in vegetable oils. Some phystosterols, especially those with an ethylidene group in their side chain, have been found to inhibit oxidative degradation and polymerization of unsaturated fatty acids during high temperature heating. The objective of this research was to determine the fate of phytosterols in vegetable oils with varying fatty acid composition used for frying. High oleic sunflower, corn, hydrogenated soybean, expeller pressed soybean, and expeller pressed low linolenic acid soybean oil were used for frying potato chips in a pilot plant-scale continuous fryer for 9 hours. The same oils, and an additional regular soybean oil were also used in a consumer-sized batch fryer to fry tortilla chips at 180 deg C for 35 hours. Phytosterols were measured at various timepoints by GC. The formation of polymerized triacylglycerides (pTAGs) was also followed by HPLC-size exclusion chromatography. In the continuous frying system, phytosterol loss was highest (~6%) in expeller pressed soybean oil, followed by corn oil, high oleic sunflower oil, and the expeller pressed low linolenic soybean oil. The rate of pTAG formation was highest in the expeller pressed soybean oils, followed by the corn and high oleic sunflower oil, and finally, the hydrogenated soybean oil. In the batch frying experiment, phytosterol loss was highest in corn oil (15.7%) followed by the hydrogenated and regular soybean oils, whereas the expeller pressed low linolenic soybean oil and the high oleic sunflower oil showed little to no loss. Formation of pTAGs during batch frying was highest (10% after 35 hr) in the regular and expeller pressed soybean oil, but remained below 4% in the other oils. In conclusion, phytosterol loss in a continuous fryer seems to be related to the degree of unsaturation of the oils. However, in the batch frying system, phytosterol loss was unrelated to the degree of unsaturation in the oils. Overall loss of phytosterols in both systems was low, indicating that these compounds are relatively stable to frying, and thus may confer some anti-degradative activity after other antioxidant constituents have been destroyed.