MEASUREMENT OF EXTRUSION EFFECTS BY VISCOSITY PROFILE USING THE RAPIDVISCOANALYSER

Extrusion processing for cereal-based products typically relies on ass ociating process responses with product qualities. Direct measurements of the product such as moisture, color, expansion, and cell size, etc . are very limited and general. The Rapid ViscoAnalyser (RVA) was used to directly measure the transformation of starch in products made by twin-screw extrusion. Samples representative of a progressively greate r cook were produced by controlling the water feed rate, or in-barrel moisture content, from 29 to 15% at two different barrel temperatures. Extrudate samples from formulations based on corn, rice, and wheat we re analyzed by RVA and the viscosity profiles compared to typical oper ational information such as torque and expansion. RVA was far more sen sitive and descriptive of processing effects caused by water content a nd thermal/mechanical inputs. Small changes in torque resulted in larg e differences in product, however, these differences were detected by RVA analysis. A strong correlation was found between the RVA viscosity data and torque as well as expansion characteristics. RVA analysis pr ovides a rapid method for directly measuring extruded products for dia gnostic, production, and product development applications.