Effects Of Twin-Screw Extrusion On Active Ingredients And Antioxidant Properties Of Astragalus Membranaceus

Twin-screw extrusion is a new technology used in the processing of food and agricultural and sideline products.It has the advantages of changeable process,continuous production and wide adaptability of raw materials.The application of this technology can change the physical and chemical properties of products,and promote the comprehensive development and the utilization of products.Astragalus Mongholicus Bunge is an important medicinal and edible plant of Leguminosae,which has a variety of pharmacological activities.In this experiment,A.mongholicus was used as raw material for the twin-screw extrusion to study the effects of material moisture content,screw speed and barrel temperature on the active ingredients,physical properties and antioxidant properties.The results are as follows:(1)After twin-screw extrusion,the content of effective components of A.mongholicus changed significantly.The contents of the total flavonoids,the total saponins and the calycosin-7-glucoside that extracted from A.mongholicus were affected by the moisture content of material,the screw speed and the barrel temperature.The optimum technological conditions for the extrusion of the total flavonoids content were 26%of the material moisture content,120℃ of the barrel temperature,and 180 rpm of the screw speed.The optimum technological conditions of the total saponins extrusion were 27%of the material moisture content,105℃ of the barrel temperature and 125 rpm of the screw speed.The optimum extrusion conditions for the content of the calycosin-7-glucoside were 25%of material moisture content,125℃ of the barrel temperature and 200 rpm of the screw speed.The optimized value of the total flavonoids content in A.mongholicus extrusion(3.22 mg/g)had no significant difference compared with the raw material,but the total saponins content(19.59 mg/g)and the calycosin-7-glucoside(0.5186 mg/g)were lower than the raw material.(2)Twin-screw extrusion affected the expansion rate and the water solubility index of the extrudates.When the extrusive conditions at 24%of the moisture content of the material,275 rpm of the screw speed and 135℃ of the barrel temperature,the extrusion rate was the highest up to 66.53%.The water solubility index was the largest up to 35.29%when the conditions were material moisture content of 21%,barrel temperature of 135℃ and screw speed of 200 rpm,which was higher than that of the raw material up to 32.8%.(3)After extrusion,the antioxidant properties of A.mongholicus was changed significantly.The DPPH radical scavenging rate was the highest when the conditions were at 27%of the material moisture content,120℃ of the barrel temperature,and 125 rpm of the screw speed.The hydroxyl radical scavenging rate was the highest when the conditions were at 24%of the material moisture content,120℃ of the barrel temperature,and 200 rpm of the screw speed.The reducing power was the highest when the conditions were at 24%of the material moisture content,120℃ of the barrel temperature was,and 200 rpm of the screw speed.The three antioxidant indexes were improved 16.72%,27.99%and 132.86%compare with the raw material,respectively.