Extraction of Visceral Oil from Yellow Croaker and Mass Transfer Modeling of Its Palmitic Acid Enrichment by Low Temperature Crystallization

With the lyophilized viscera as material and extraction rate as index,the extraction rate of yellow croaker fish oil by dilute alkali hydrolysis method,enzymatic hydrolysis method and microwave-assisted extraction was studied. The fatty acids composition of fish oil was detected by gas chromatography to analyze the differences in fish oil extracted by three methods,and the differences in the content and distribution of fish oil fatty acid were analyzed. The results showed that the dilute alkali hydrolysis method had the highest extraction rate of viscera oil(accounted for 84.26%±5.15%),and the highest level of DHA,ARA,sn-2 palmitic acid(accounted for 39.94%±1.11%)and relative palmitic acid(accounted for 50.55%±1.06%),which was most suitable as raw material for enrichment in palmitic acid. Then,the best conditions for palmitic acid enrichment were determined with palmitic acid as index by crystal mass transfer model of low temperature crystallization. The correlation coefficients of the predicted crystal mass equation and the palmitic acid mass equation were R²>0.97 and R²>0.94,respectively. The optimal conditions for low temperature crystallization were:Oil-to-hexane ratio 1:6,low temperature -40℃,and crystallization time 2.6 h,in which the yield of palmitic acid was 80.50%±4.39%,the content of palmitic acid was 42.62%±2.67%,and the content of sn-2 palmitic acid was 68.19%±1.47%. The model accurately simulated palmitic acid enrichment of visceral oil and the enriched glyceryl palmitate has the potential to be applied to infant milk powder to increase the sn-2 palmitic acid.