Impact of Frying on Changes in Clam (Ruditapes philippinarum) Lipids and Frying Oils: Compositional Changes and Oxidative Deterioration

The current study shows the compositional changes and oxidation development of clam ( Ruditapes philippinarum , R. philippinarum ) lipids and frying oils when subjected to different processing conditions. Parameters measured include acid value, peroxide value (POV), thiobarbituric acid-reactive substances (TBARS), total oxidation (TOTOX), lipid classes, fatty acid composition, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) contents together with major glycerophospholipid (GP) molecular species. Deep-fat frying increased triacylglycerol (TAG) content and decreased the contents of PC, PE, and GP molecular species in clam in a time-dependent manner. Meanwhile, minor amounts of free fatty acids, diacylglycerols, monoacylglycerols, and polar lipids were detected in frying oils, indicating lipid migration between the clam and frying oils. The time-dependent increase of POV, TBARS, and TOTOX in fried clams and frying oils with concurrent reduction of docosahexenoic acid and eicosapentaenoic acid indicates extensive oxidative degradation of clam lipids. Moreover, the moisture-rich clam aggravated the deterioration of frying oils. Consequently, deep-fat frying significantly altered the lipid profile and decreased the nutritional value of clams.