Lipids from cephalothorax and hepatopancreas of Pacific white shrimp (Litopenaeus vannamei): compositions and deterioration as affected by iced storage.

Lipids from cephalothorax and hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) stored in ice for up to 6 days were extracted and characterised. The extraction yields of lipids from hepatopancreas (10.65-12.64%) were higher than those from cephalothorax (2.59-2.88%). However, no changes in the extraction yield were observed during the storage (p>0.05). The carotenoid contents of lipids from cephalothorax and hepatopancreas slightly increased within the first 2 and 4 days of iced storage (p<0.05), respectively, but decreased thereafter (p<0.05). With increasing storage time, a progressive formation of hydroperoxide was found as evidenced by the increase in the absorbance band at 3600-3200 cm(-1) in Fourier transform infrared (FTIR) spectra, and increased peroxide values (PVs) (p<0.05). The increases in thiobarbituric acid reactive substances (TBARS), p-anisidine value (AnV) and free fatty acid (FFA) content of lipids were noticeable when iced storage time increased (p<0.05). Those changes indicated that lipid oxidation and hydrolysis occurred in both samples. Phospholipids (PL) were the major components in lipids from cephalothorax (82.51% of total lipids). Nevertheless, lipids from hepatopancreas contained triglyceride (TG) and PL as the dominant components (45.35% and 38.03% of total lipids, respectively). A decrease in the TG content with a concomitant increase in free fatty acid was observed at the end of storage (day 6) (p<0.05). Decreases in unsaturated fatty acids, especially eicosapentaenoic acid (EPA; C20:5(n-3)) and docosahexaenoic acid (DHA; C22:6(n-3)) were noticeable at day 6 of storage (p<0.05). Thus, the extended storage time resulted in the enhanced deterioration of extracted lipids.