| China is abundant in freshwater fishes, and the production was 2009 million tons in the year 2005. In freshwater fishes processing, 50%-70% wastes, such as fish head, fish viscera and abdominal meat, which were rich in fish oil, will be produced. In this paper, freshwater fishes wastes, as raw material, was used to extract fish oil, and effects of diffrent methods and conditions on the extraction ratio and quality of fish oil were studied. At the same time, fatty acid composition of fish oil from different freshwater fishes' wastes was studied as well. Based on this, fish oil extracted from fish's wastes was refined, and then the refined oil was microencapsuled by spray-drying, during which the optimum condition for microencapsulation was inverstigated. The main results were summarized as follows:(1) The process of extracting fish oil by diluted alkali hydrolysis was studied. Extraction temperature, hydrolysis pH, salt precipitation temperature, salt precipitation time, salt dosage and solid-liquid ratio had a significant influence on extraction rate and quality offish oil. The optimum processing parameters were: solid-liquid ratio 1:1, pH8.5, extraction temperature 45℃, precipitation temperature60℃, salt dosage 12%, and salt precipitation time 2min.(2) Condition of Protemax hydrolysis processing were inverstigated by orthogonal experiment. Extraction rate and quality of fish oil, such as pereoxide value, acid value and iodine value, were significantly affected by hydrolysis temperature, initial pH, enzyme dosage and acting time. The results showed that, the optimum processing parameters were pH7.5, enzyme dosage 2000U/g, and hydrolyze at 55℃for 3h.(3) The extraction rate and quality of fish oil extracted by diluted alkali hydrolysis, Protemax hydrolysis, Alcalase hysrolysis and endogenous enzymes hydrolysis separately were compared. The quality of fish oil extracted by proteinase hydrolization method was worse than that of fish oil extracted by diluted alkali hydrolysis, but the extraction rate was much higher, especially by Protemax hydrolysis and Alcalase hysrolysis methods, the extraction rate of which were 82.41% and 82.99% respectively, and the extraction rate of endogenous enzymes and diluted alkali hydrolysis were 72.30% and 62.48% respectively. The content of n-3 series polyunsarurated fatty acids by Protemax hydrolysis and diluted alkali hydrolysis was highest, which were 33.34% and 32.78% respectively, and the content of n-3 series polyunsaturated fatty acids by Alcalase and endogenous enzymes were 33.16% and 29.26% respectively. The content of EPA and DHA by Protemax, diluted alkali hydrolysis and Alcalase were 3.41%, 3.08% and 2.05% respectively, but EPA and DHA could not be detected from fish oil by endogenous enzymes.(4) Basic physicochemical indexes of silver carp, grass carp and crucian carp' wastes were detected, and the fatty acid composition of fish oil from these wastes was analysised by GC-MS. The results showed that, the main component of freshwater fishes' wastes was water, and the rest were fat and protein. Grass carp viscera and silver carp viscera were richer in oil(grass carp 34.87%,silver carp 17.37%), and they had less protein(grass carp 8.99%, silver carp 5.67%), which was propitious to extract fish oil. The content of n-3 series polyunsaturated fatty acids of fish oil from grass carp was highest, which was 51%, and silver carp viscera was 36%.(5) Microencapsulation of fish oil by spray-drying was studied. The suitable support material was the mixture of acacia gum, casein andβ-cyclodextrin, the suitable proportion of which was 3:1:4. By orthogonal test, the infected sequence of factors was: solids concentration 35%, the propotion of fish oil 30%, emulsification temperature 50℃, inlet air temperature 220℃, feed flowrate 300mL/h, spray pressure 0.35MPa. Fish oil microcapsule produced by the optimum condition had high encapsulation rate and yield. The surface of fish oil microencapsule had a globular structure with depression phenomena, and the size of fish oil microencapsule was about 1μm～10μm.
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