Research On Aqueous Enzymatic Extraction Of Rapeseed Oil Assisted By Extrusion

As the second largest edible oil in China,rapeseed oil has high nutritive value with rational unsaturated fatty acid and lipid concomitant.It has physiological functions such as cholesterol-lowering,anti-cancer,antioxidant-enhancing and so on.It is one of the most beneficial edible vegetable oils for human health.The disadvantages of mechanical press such as the low oil yield,the poor quality of rapeseed meal and the disadvantages of solvent extraction such as the loss of oil quality and high production environment requirements are all need to be solved.Aqueous enzymatic has the advantages of mild extraction conditions,good quality of crude oil and high utilization rate of by-products.But there are still some disadvantages such as low extraction rate and long production period,which makes it difficult to realize the industrial production.In order to improve the extraction rate,quality of rapeseed oil and shorten the production period,a study on the extraction of rapeseed oil by aqueous enzymatic extraction assisted by extrusion was carried out.The main research contents and results are as follows:1.Optimization of extrusion parameters of extracting rapeseed oil by extrusion-assisted aqueous enzymatic methodUnder the condition of fixed enzymatic hydrolysis,the effects of barrel temperature,feed speed,screw speed and the adding amount of water on oil extraction rate were studied through single factor and orthogonal experiments.The results showed that the degrees of extrusion parameters on oil extraction rate were barrel temperature > feed speed > the adding amount of water > screw speed.The optimum technological parameters of extrusion were as follows: barrel temperature 90 ?,feed speed 12 kg/h,the adding amount of water 10%,screw speed 210 r/min.Under the above-mentioned optimum conditions,the extraction rate of rapeseed oil was 80.834%.2.Technological optimization of enzymatic hydrolysis of rapeseed pretreated by extrusionBy using the rapeseed pretreated by extrusion as raw material and the oil extraction rate as the index,the kind and ratio of enzymes were studied.On this basis,the influence of the enzymatic hydrolysis conditions on the oil extraction rate were investigated by using the single factor test and response surface optimization test.The results showed that the suitable enzyme for rapeseed pretreated by extrusion were selected as neutral protease,pectinase and amylase,and the appropriate proportions of neutral protease,pectinase and amylase were0.573:0.315:0.112.The results showed that the oil extraction rate of 92.333% was obtained under the optimum enzymatic hydrolysis conditions: temperature 50 ?,p H 6,the ratio of material to liquid 1:4,the complex enzyme adding amount 2%,the enzymolysis time 4 h.3.Study on emulsion demulsification technology in extracting rapeseed oil by extrusion-assisted aqueous enzymatic methodBy using the demulsification rate as the index,the emulsion produced in extracting rapeseed oil by extrusion-assisted aqueous enzymatic method was treated by the compound demulsification method.On the basis of single factor test,the optimum technological conditions of emulsion demulsification were determined by orthogonal test: p H value 3,shear speed 6000 r/min,water bath temperature 90 ?.Under these conditions,the demulsification rate of emulsion could reach 96.389%.The total extraction rate of rapeseed oil reached 97.807%.4.Evaluation on the quality of rapeseed oil extracted by extrusion-assisted aqueous enzymatic methodCompared with the rapeseed oil extracted by squeezing method and leaching method,sensory quality,the physical and chemical indexes,and composition and content of fatty acid of the rapeseed oil extracted by extrusion-assisted aqueous enzymatic method was measured and evaluated.The results showed that the basic physicochemical indices of three kinds of oils were all conformed to the national standard.There were no obvious differences on transparency,smell and taste of the oils.The color of the rapeseed oil extracted by aqueous enzymatic method was lighter than that of the other two oils,which was close to that of refined rapeseed oil.There were no obvious differences on the moisture and volatiles and relative density of the oils.The content of insoluble impurity,peroxide value,saponification value and phospholipid of rapeseed oil extracted by extrusion-assisted aqueous enzymatic method were 0.017%,1.304 mmol/kg,176.645 mg/g and 0.031%,which were significantly lower than the other two oils.The iodine value was significantly lower than that the rapeseed oil extracted by squeezing method.The acid value of rapeseed oil was2.238 mg KOH/g,higher than the other two oils.The extraction methods had no effect on the fatty acid composition of rapeseed oil,but the content of fatty acid was slightly different.The contents of linoleic acid,arachian acid,linolenic acid,and arachidonic acid in aqueous enzymatic rapeseed oil were 13.760%,0.585%,4.780%,11.570%,which was significantly higher than rapeseed oil extracted by squeezing method.The contents of palmitic acid and stearic acid were 3.715% and 1.745%,which were significantly lower than the other two oils.