| The materials pretreated by extrusion were half-wet corn germ in this paper.According to optimize the parameters of screw by pressure and torque when extruder reached steady state,and establish kinetic equation to optimize the extraction conditions.We get the following conclusion through test:1 The quadratic orthogonal rotating combination test design involving 4 factors and 5 levels.Test results were got to study the effects of parameters of screw for steady state of extruder.We can get the final optimization results by analysising response surface: choke ring diameter is 92 mm;the length of ? is 16 mm;Thread angle is 7.10 °;the screw rotation speed of 180 r/min.Under the optimal parameters,the oil content was 18.85%,the coefficient of variation of pressure was 0.0716,the shear strength was 12.57 N,coefficient of variation of torque was 0.0937.2 The extraction kinetics equation model basis on Fick's first law and Fick's second law as a theoretical was set up.In the process of extraction,technological parameter were extraction temperature,extraction time and flow ratio,which have important effects for the residual oil ratio.We can build the extraction kinetics equation according to study the relationship of technological parameter and residual oil ratio.According to the extraction kinetics equation,the optimum technological parameter can be calculate: the extraction time was 110 min,the flow ratio was 6 mL/min,extraction temperature was 50 ?.3 Acid value of the extruded corn germ was between 2.07 to 3.89 mg/g,iodine value was between 107 to 132.77 g/100 g,saponification value was between 187.36 to 194.8 mg/g,insoluble impurities was between 0.1705 to 0.1995%,which were in line under the national safety standards.The images under the observation of scanning electron microscopy can be seen that the materials in the steady extrusion condition were more homogeneity in structure than other conditions.Oiled channel was apparent,and the extraction efficiency was higher. |
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