Effect of Various Hot-Air Drying Processes on Clam Ruditapes philippinarum Lipids: Composition Changes and Oxidation Development

Clam Ruditapes philippinarum was processed by hot-air drying and the changes of its lipids were evaluated by analyzing lipid classes, phospholipid classes, fatty acids, as well as oxidation parameters including peroxide value (POV), thiobarbituric acid-reactive substances (TBARS) value, total oxidation value (TOTOX), and oxidation test (OXITEST). The hot-air drying process reduced the contents of triacylglycerol, phosphatidylcholine, and phosphatidylethanolamine, indicating the hydrolysis of lipids. Meanwhile, the hot-air drying process significantly decreased the proportion of n-6 polyunsaturated fatty acid (PUFA), and consequently increased the PUFA ratio of n-3/n-6. Interestingly, the POV, TBARS and TOTOX decreased after the hot-air drying process. However, significant decline of the induction period for the dried clam tissue at elevated temperatures indicated their higher oxidation level, poor oxidative stability and reduction of shelf-life. Therefore, OXITEST method turned out to be an effective tool for estimating the level of lipid oxidation for hot-air dried clam.