Changes in fatty chain compositions of ether and ester glycerophospholipids of Japanese oyster Crassostrea gigas during frozen storage.

Abstract

Changes in alkenyl, alkyl, and acyl chain compositions of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) subclasses of Japanese oyster Crassostrea gigas (Thunberg) during frozen storage were investigated. During storage at -20°C for up to 12 months, the alkenylacyl- and diacyl-PE, major constituents of PE, decreased to 82.1% and 71.2%, respectively, of their initial contents (96.9mg/100g and 53.0mg/100g total wet organic tissues, respectively). In the case of PC homologues, the diacyl-PC was the major constituent, of which content decreased to 54.7% of its initial contents (244mg/100g) during storage. The diacyl-PC and -PE were lost more rapidly than the alkenylacyl- and alkylacyl-PC and -PE. In the alkenylacyl- and alkylacyl-PE and -PC, percentages of relatively shorter alkenyl or alkyl chains such as 14:0 and 16:0 or 18:0 on the sn-1 positions of glycerol moieties decreased at higher rate than those of the corresponding longer chains such as 18:0 and 20:1. In the alkenylacyl-PC, alkylacyl-PE (or-PC), and diacyl-PE (or-PC), the shorter acyl chains on the sn-2 positions were lost more rapidly than the longer and polyunsaturated fatty chains such as 20:5n-3, 22:6n-3, and 22:2 non-methylene interrupted diene (NMID) did. In the case of alkenylacyl-PE, loss of 20:5n-3 occurred at highest rate among the prominent aryl chains on the sn-2 position. These changes in fatty chain compositions seemed to be due to both oxidation and enzymatic hydrolysis of the PE and PC homologues.