The Study On The Extrusion Processing And Rheological Properties Of Coarse Grain Solid Beverage

Coarse grain solid beverage was developed using DS32-Ⅱ twin-screw extrusion with the blend of the powder of red bean, corn, glutinous rice, oatmeal, adlay and buckwheat. The effects of screw speed, barrel temperature, water content in raw materials and feed speed on quality indices including texture, expansion degree, blue value(BV) and water absorbing index(WAI) of extruded powder were investigated. Based on these results, with WAI as response value, An response surface design was used to determine the optimal process parameters as follows:screw speed of151r/min, barrel temperature of184℃, water content in raw materials of15.53%, and feed speed18Hz (1Hz=1.7r/min).Under the proposed optimized conditions,503%of WAI was achieved. The predicted values for optimization process conditions were in good agreement with experiment data. Rheological properties research showed that:Suspension liquid of extruded powder is a typical pseudoplastic fluid and thixotropic fluid. There are four factors contained temperature, granularity, mass fraction of extruded powder and adding food colloids, which affect the change of suspension liquid viscosity. Temperature-Adhesiveness model can describes the effect of temperature on the suspension" viscosity. At the same time, using the Power-Law equation Herschel-Bulkley equation and Casson equation to describe the rheological properties of suspension liquid, The result showed that Power-Law equation" fitting coefficient is of the highest, with the increase of mass fraction, Suspension liquid has tended to become fluid with yield stress. Extrusion can reduce the crystallinity of starch in grains powder, Extruded powder reconstitution process of water infiltration rate and the change of viscosity may be the main cause of agglomeration, the change of consistency cause poor palatability.