Changes in lipids of whole and minced rayfish (Raja clavata) muscle during frozen storage

The effects of the storage temperature (-18 degrees C and -40 degrees C) and the addition of butylhydroxytoluene (BHT) on the different classes of lipids (phospholipids, triacylglycerides, free fatty acids, sterols and sterol esters plus waxes) and the fatty acid composition of minced (8 and 12 mm) and whole rayfish wing muscle stored for 1 year in the frozen state were studied. The phospholipid content decreased significantly and the free fatty acid content increased significantly at both storage temperatures, but more pronounced, at -18 degrees C. Significant differences were found between phospholipid and free fatty acid contents of the minced and the whole samples, which again were more pronounced at -18 degrees C. A significant increase of the major fatty acids (22:6n-3 and 16:0) was observed after 1 year in the frozen state. Significant differences were also obtained between the samples stored at -18 degrees C and at -40 degrees C; the lower the storage temperature, the higher their content. The polyunsaturated fatty acid (PUFA) content increased significantly in all the samples. Significant differences were found between the samples stored at -18 degrees C and at -40 degrees C. The lower the temperature, the higher the PUFA content. Non-significant differences were observed between the 8-mm and the 12-mm minced samples. Non-significant differences were found between the samples stored in the presence and in the absence of BHT. Mincing hastened hydrolytic and oxidative processes, which were slowed down at the lower storage temperature. Nonetheless, non-significant differences were found between both particle sizes.