Speculate on the Formation Mechanism of Nonanal and Decanal from LPC (18:1) and LPE (18:1) in the Steaming of Chinese Water Chestnut Based on the in Vitro Model Study

The in vitro models of lysophosphatidylcholine 18:1 (LPC(18:1)), lysophosphatidy- lethanolamine 18:1 (LPE(18:1)) and oleic acid were constructed by simulating the pH, LPC(18:1) and LPE(18:1) contents and steaming conditions of Chinese water chestnut (CWC). The content of nonanal, decanal and oleic acid, and peroxide value (POV) produced by the in vitro models were used as indicators to investigate the formation mechanism of nonanal and decanal from LPC(18:1) and LPE(18:1) during the steaming of CWC. The results showed that the possible mechanism of the oxidation of LPC(18:1) and LPE(18:1) to form nonanal and decanal was as follows. First of all, the C8 and C11 positions close to the double bond on the unsaturated acyl chain of LPC(18:1) and LPE(18:1) lost H respectively, and then formed R·. In the second step, the R· directly reacted with O2 and H to form 8-hydroperoxide (8-ROOH), or reacted with O2 and H to form 9-hydroperoxide (9-ROOH) and 10-hydroperoxide (10-ROOH) after electron rearrangement. Finally, 8-ROOH split homogeneously to form decanal, 9-ROOH and 10-ROOH split homogeneously to form nonanal. The results can provide scientific reference for the formation mechanism of flavor substances and the regulation of flavor quality of fruits and vegetables.