Analysis and Comparison on the Quality and Volatile Flavor Components of Crude Fish Oil from the Viscera of Three Freshwater Fishes

In order to improve the high-value utilization of by-products from freshwater fish processing, crude fish oil was extracted from the viscera of three common freshwater fishes (grass carp, black carp and silver carp), and the physicochemical indexes, fatty acid composition as well as volatile flavor components were monitored. The findings indicated that a best quality was observed in black carp oil due to its lower peroxide value, acid value, moisture and volatile matter, anisidine value and unsaponifiable matter, followed by silver carp oil and grass carp oil. A total of 27 fatty acids were detected in silver carp oil accompanied by 22 and 16 fatty acids in black carp oil and grass carp oil. The most preponderant fatty acids in three crude fish oils were palmitic acid (C_16:0), oleic acid (C_18:1n-9c) as well as linoleic acid (C_18:2n-6c), and a highest nutritional value was observed in silver carp oil. The 66 volatile compounds involving 17 hydrocarbons, 7 alcohols, 15 aldehydes, 3 ketones, 8 esters, 10 acids, 3 phenols and 3 other components were detected in three crude fish oils. The highest level of volatile substances in grass carp oil, black carp oil and silver carp oil were separately phenols (59.86%), alcohols (53.23%) and acids (27.64%). Additional, aldehydes, alcohols and phenols were found to be the prominence among the 10 key flavor components obtained from the three crude fish oils. Trans-2,4-decadienal, nonanal, trans-2,4-hepadienal, phenylacetaldehyde, 1-octanene-3-alcohol were the main fishy and oil flavor substances in crude fish oils.