Temporal Changes of Total Lipids in Flaked Dried-Bonitos ('Katsuo-Kezuribushi' in Japanese) During Storage

Abstract

Flaked dried-bonitos manufactured from two groups of fresh bonitos (less than 3kg and average 6kg as a perishable fish) were stored at 20°C, 5°C and-25°C for 150 days, then temporal changes (chemical properties, lipid and fatty acid compositions) of lipids extracted from various phases were investigated. The results may be summarized as follows :
1) Total lipids contents (g/100g dried matter) decreased as the time goes, particularly this change was remarkable (9. 12→8.92g) in the case of 20°C storage, in brief, storage at low temperature was effective to control for lipid alteration.
2) Compound lipid fraction contents (g/100g dried matter) decreased during storage, while neutral lipid fraction contents increased a little. And above changes were observed at three storage temperatures, but were slightly observed in the case of-25°C storage.
3) Regarding changes of each lipid contents composed of neutral and compound lipid fractions, decrease of triacylglycerol, phosphatidylcholine and phosphatidylethanolamine contents (g/100g dried matter), and increase of free fatty acids contents during storage were observed at all storage methods, but flaked dried-bonitos stored at-25°C had smaller these changes than those at stored 20°C and 5°C
4) On the changes of main fatty acid composition (weight %) of total lipids, neutral lipid fraction and compound lipid fraction, decrease of highly polyunsaturated fatty acids contents as 22 : 6 acid and increase of saturated fatty acids contents as 16 : 0 acid were observed at all storage methods, particularly, these changes were larger in the case of 20°C storage. Besides, changes of main fatty acid composed of compound lipid fraction were notable as compared with that of neutral lipid fraction.