Abstract
The method of identification the quality of fish oil by the analysis of a glass transition shift was suggested. Unique properties of “unfreeezable” triacyglycerides (TAG), which contain polyunsaturated fatty acids, were used as a marker of the quality for extra-fine fish oils. Melting peaks of fish oils were significantly wider and melting energies were significantly lower, when compared with plant oils (50.0 kJ kg-1 vs. 72.0 kJ kg-1). The average concentration of “unfreezable” fraction was between 40.0 and 60.0 % for fresh oil extracted from commercial fish species such as Atlantic Herring, Mackerel, Trout and Salmon. The oxidation process resulted in a significant decrease of “unfreezable” fraction to 30.6 %. The melting energy of fish oils increased up to 60.0 % due to the significant accumulation of oxidation products.