Changes in lipids during the storage of krill (Euphausia superba Dana) at 3 degrees C.

Lipid content and composition (classes), susceptibility to UV-catalysed oxidation and carotenoid content were determined in Antarctic krill (Euphausia superba Dana) stored for 72 h at 3 degrees C. Phospholipids making up 80% of krill lipids were observed to undergo the most drastic changes during storage. After 72 h of storage, their content dropped by about 20%; the largest drop was recorded in phosphatidylcholine, its content being reduced by almost half. The amount of free fatty acids increased to about 6% of lipids. No degradation was observed in triacylglycerols, diacylglycerols, and wax esters. Monoglycerides did not appear. The UV-catalysed lipid oxidation rate decreased with deteriorating freshness of krill, as evidenced by a slower oxidation reaction, much lower oxidation maximum attained by lipids from spoiled krill, slower carotenoid decomposition, slower coloration of lipids and a slower absorbance increase at 320 nm. As no significant differences were found between iodine numbers and the carotenoid content of the samples tested, differences in the oxidation rate can be explained by hyperoxide decomposition brought about by products of phosphatidylcholine break-down.