High‐performance size‐exclusion chromatographic studies on polar components formed in sunflower oil used for frying

Abstract

Thermoxidative and hydrolytic alterations of a sunflower oil used in sixty repeated and discontinuous deep‐fat fryings of potatoes were evaluated by column and high‐performance size‐exclusion (HPSE) chromatography. Successive fryings of potatoes in sunflower oil, without turnover of fresh oil during the performance of fryings, increased the level of total polar components in the oil from 3.75% to 27.28% (w/w). Triglyceride polymers, triglyceride dimers, oxidized triglycerides and diglycerides increased after sixty fryings 89.8, 21.8, 4.9 and 1.7 times, respectively. These increases were well correlated with the number of fryings. However, there was not significant correlation between levels of free fatty acids and the number of fryings. Polar compounds were highly (r=0.9691) and significantly (P<0.01) correlated with triglyceride polymers and also highly (r=0.9969 and r=0.9738) and significantly (P<0.01) with triglyceride dimers and oxidized triglycerides, respectively. Nevertheless polar compounds were not significantly correlated with free fatty acids. Data suggest that an intensive thermoxidative rather than a hydrolytic process takes place in experimental deep‐fat frying of potatoes.