Cyclic fatty acid monomers and thermoxidative alteration compounds formed during frying of frozen foods in extra virgin olive oil

The measurement of polar content and specific polar compound distribution was used to evaluate the alteration of an extra virgin olive oil (EVO) used 20 times to fry frozen foods employing two methods of frying (with or without oil replenishment during frying). In addition, cyclic fatty acid monomers (CFAM) were quantified and identified throughout the 20 frying operations. Total polar content and specific polar compounds increased in the used oil (with or without replenishment). Nevertheless, frequent replenishment (FR) permits a higher number of fryings because of a dilution effect that helps maintain lower amounts of polar and specific alteration compounds than when null replenishment (NR) was used. CFAM were absent in the unused EVO, but appeared in the oil bath as a consequence of oil heating. The total CFAM concentration was higher when the oil was used with the NR method. Cy clopentyl fatty acids were more abundant than cyclohexyl ones. The data suggested that the FR frying is more appropriate to maintain the duality of the oil during frozen food frying.