Twin screw extrusion of peach puree: Rheological properties and product characteristics

A semi-empirical, nonlinear model was developed to incorporate the effects of extruder operating conditions (temperature, moisture, and shear rate) on viscosity of peach puree in a lab-size twin screw extruder. A power law de pendency for shear rate, an exponential dependency for moisture, and a modi fied first order transform function for temperature effects were employed. The proposed model fit the experimental data well. Motor torque and Specifi c Mechanical Energy (SME) were significantly affected by all extruder opera ting conditions, Experimental apparent viscosity varied from 40 to 130 Pa.s , depending on the operating conditions. Color indicatives (L, a, b) and ex trudate density were mainly influenced by the moisture content. Water activ ity was only influenced by moisture.