Effect of deep-fat frying on phytosterol content in oils with differing fatty acid composition

The objective of this study was to determine the fate of phytosterols in vegetable oils with varying fatty acid composition used for frying. High oleic sunflower (HOSun), corn (Corn), hydrogenated soybean (HSBO), expeller pressed soybean (ESBO), and expeller pressed low-linolenic acid soybean oil (ELLSBO) were used for frying potato chips in a pilot plant-scale continuous fryer. The same oils, and regular soybean oil (SBO) were also used in intermittent batch frying of tortilla chips. Phytosterols were measured in oils collected at various times during frying by GC to determine their loss. The formation of polymerized triacylglycerides (PTAGs) and total polar compounds (TPC) were analyzed to determine the extent of oil degradation. In the continuous frying system, phytosterol loss ranged between 4 and 6% in ESBO, ELLSBO, HOSun, and Corn, with no loss in HSBO. PTAGs and TPC were highest in ESBO and ELLSBO, followed by Corn, HOSun, and HSBO. In the batch frying experiment, phytosterol loss ranged from 1 to 15%, and was highest in Corn followed by SBO and HSBO. There was no significant loss of phytosterols in ESBO, ELLSBO, and HOSun. Formation of PTAGs and TPC during batch frying was highest in SBO and ESBO, followed by Corn, ELLSBO, HOSun, and HSBO. In conclusion, phytosterol loss in both the continuous fryer and in the batch frying system appeared to be unrelated either to fatty acid composition, or to the extent of oil degradation.