Quality Analysis And Extraction Technology Of Tuna Oil By Supercritical CO₂

Tuna will produce by-products such as fish head,fish bones and internal organs during processing,accounting for 50?70%of the total quality of tuna.These by-products are generally used to produce fishmeal or directly discarded,which wastes resources and forms new environmental pollution factors.Therefore,improving the processing and utilization of tuna by-products is a new direction of current research.In order to maximize the use of tuna processing by-products,this paper analyzed the basic nutrient composition of tuna fish head and evaluated the nutritional value;extracted the tuna fish oil with supercritical CO₂,and analyzed the physicochemical properties and fatty acid composition of fish oil;The changes of peroxide value,acid value and volatile odor of fish oil under storage conditions?40,25,4,-20°C?,and the oxidative stability of fish oil and the shelf life of fish oil were analyzed by Rancimat method and DSC method.The findings are as follows:?1?Tuna head is rich in crude protein,crude fat and minerals;the crude protein content of tuna head is higher,the proportion of essential amino acids is reasonable and the nutritional value is higher,while the nutritional value of protein in fish skin and bone is relatively low.Fish head is rich in polyunsaturated fatty acid?PUFA?,in which the total content of docosahexaenoic acid?DHA?and eicosapentaenoic acid?EPA?is between20.55%and 27.71%,and the ratio of n-6 to n-3 PUFA is between 0.13 and 0.29.The tuna head is also rich in mineral elements,such as Ca,Fe and Zn,which are beneficial to human health.?2?The tuna fish oil was extracted by supercritical CO₂,and the mathematical model of extraction process was established to optimize the extraction process parameters.Under the optimal extraction conditions,the fish oil extraction rate can reach 97.66%when the material filling amount is 162.5 g,the extraction temperature is 30°C,the extraction pressure is 22.5 MPa,and the extraction time is 180 min.The sensory and physicochemical properties of the fish oil can reach the standard of refined fish oil..The fatty acid analysis of the fish oil shows that the saturated fatty acid?SFA?in fish oil is mainly palmitic acid?17.45%?,stearic acid?3.53%?,lauric acid?3.63%?;monounsaturated fatty acid?MUFA?is oleic acid?24.99%?palmitoleic acid?5.86%?and peanut oleic acid?1.6%?;?3?polyunsaturated fatty acids?PUFA?dominated by DHA?24.79%?and EPA?4.71%?,n-6 and n-3 The PUFA ratio is 0.2,which is much lower than the United Nations Food Agriculture Organization/World Health Organization?FAO/WHO?rating.Therefore,the fish oil has a high nutritional value.?4?The volatile components of tuna oil during storage were analyzed by electronic nose.The volatile odor of tuna oil did not change significantly at low temperature?4,-20??,but changed significantly at high temperature?25,40??.The variation trend of volatile odor was basically consistent with its acid value and peroxide value.?5?The oxidative stability of tuna fish oil was analyzed using a Rancimat grease oxidation meter and a differential scanning calorimeter?DSC?.According to the Rancimat method,the shelf life of tuna fish oil at 25?was 12 days and the shelf life at 40?was 2days.The DSC curve analysis of tuna fish oil shows that the shape and trend of DSC curves are similar at different heating rates.The thermal oxidation activation energy of fish oil was calculated to be 125.01 KJ/mol by Flynn-Wall-Ozawa method.The thermal oxidation activation energy of fish oil was calculated by Kissiger method to be 121.60KJ/mol.The two methods have good consistency and thermal oxidation.The activation energy value of about 120 indicates that the fish oil has certain oxidative stability.