Optimization Of Shrimp Oil Extraction Techniques And Related Quality Evalutation Of Crayfish By-products

In order to explore extracting shrimp oil from crayfish by-products by the enzymatic hydrolysis method,the single factor and orthogonal test methods were used to screen out the optimal process parameters.At the same time,in order to compare the effects of different drying methods on the quality of shrimp oil and the quality changes of shrimp oil before and after refining,the physical and chemical indicators,visible spectrophotometer,gas chromatography-mass spectrometer were used to determine the oil quality of crude and refined shrimp oil,the oil quality analysis contained the physical and chemical indicators,the ability to remove DPPH,volatile constituents and the relative content of fatty acids.(1)The crayfish by-products were treated by electrothermal blowing drying,vacuum drying and vacuum freezing drying,respectively.The three crude shrimp oil was extracted from the three dried by-products by the organic solvent method,and the quality characteristics of the three shrimp oil were compared.The three crude shrimp oils have stronger ability to scavenge DPPH,and are better than VE,but the acid value is high(>10.00mgKOH/g),the iodine value(<120 g/100g)and the saponification value(<180 mgKOH/g)are low.The relative content of saturated fatty acids(SFA)is higher than that of monounsaturated(MUFA)and polyunsaturated fatty acids(PUFA)in the three crude shrimp oils,and the ?EPA + DHA of the shrimp oil which extracted from the crayfish by-product treated by vacuum freezing drying has the high content(5.18%).In addition,the pyrazine(25.96%),acid(32.16%)and hydrocarbons(34.33%)is the mainly volatile substances of crude shrimp oil which extracted from the crayfish products treated by electrothermal blowing drying,vacuum drying and vacuum freezing drying,respectively.Comprehensive comparison shows that the quality of crude shrimp oil which extracted from the crayfish by-product treated by vacuum freezing drying is the best.(2)Alkaline protease enzymatic assisted method was used to extraction of shrimp oil from crayfish by-product(wet basis),the method was optimized by single factor and orthogonal test.The optimized auxiliary enzymatic parameters are bottom material water ratio 1:2,enzymatic hydrolysis pH 8.5,the amount of alkaline protease added was1.8%(based on the weight of the shrimp paste),enzymatic hydrolysis temperature 55°C,enzymatic hydrolysis time 1.5 h.the extraction rate of shrimp oil reached 90.03% under this condition.(3)The crude shrimp oil extracted by enzymatic hydrolysis method was used as raw material,and the quality characteristics of crude shrimp oil and refining shrimp oil were compared.After the crude shrimp oil refining,the color of the crude shrimp oil is lighter,the appearance is clear,the smell of shrimp is less,and the DPPH removal ability of refined shrimp oil is stronger than that of crude shrimp oil and VE,but the recovery rate of shrimp oil after deacidification is only 63.10%.With the refining of crude shrimp oil,the acid value,saponification value and peroxide value of crude shrimp oil decreased to 1.70mgKOH/g,173.88 mgKOH/g and 1.76 mmol/kg,and the iodine value increased to 92.24g/100 g respectively.In addition,the fatty acids proportion were ?SFA>?MUFA>?PUFA in crude shrimp oil and refined shrimp oil,and the total contents of EPA and DHA were 4.21%and 5.32%,respectively.A total of 47 volatile substances were detected in the two shrimp oil,and the contents of alkanes compounds were 34.50% and 44.04% in crude and refining shrimp oils,respectively.In conclusion,the quality of the shrimp oil extracted by the enzymatic hydrolysis assistant method is good,and the quality of shrimp oil is remarkably improved after refining.