Influence of fried food and oil type on the distribution of polar compounds in discarded oil during restaurant deep frying.

Deterioration of frying oil greatly affects the nutrition of fried foods. In this study, influence of fried food and oil type on the distribution of polar compounds in oils at total polar compound (TPC) of 24%, 25% and 27% was evaluated. Both food and oil significantly affected the composition of frying oil (P < 0.01) and the effect of oil was relatively more significant than that of food. Five groups of polar compounds were presented: triglyceride oligomer (TGO), triglyceride dimer (TGD), oxidized triglyceride monomer (oxTGM), diglyceride (DG) and free fatty acid (FFA). TGD and DG had the highest contents, up to 6.9%-7.5% and 8.1%-8.9% respectively, while FFA had the lowest content with 1.4%-1.7%. The compound of the greatest concern in frying oil, oxTGM, varied from 4.6% to 4.8%, when TPC reached 24%-27%. Data will be expected to provide the evidence for toxicological evaluation of fried oils and foods in restaurants.