Characterization of starch-additive interactions in starch-based systems during twin-screw extrusion

With a continued increase in numbers of extruded products on the market and with increased requirements to develop an advanced extrusion technology, it is important to be able to predict behavior of feed ingredients on the characteristics of extruded products. Thus, the effects of feed composition on the overall performance of a twin-screw extruder and the final product characteristics were investigated. Addition of ingredients such as silicon dioxide and oil to a starch-based feed not only had an effect on the rheological behavior of the dough during extrusion, but also a significant influence on the final textural and general physico-chemical properties of the extrudates, including expansion ratio, cell size, molecular degradation and degree of crystallinity. Many of the observed trends may also be drastically altered depending upon variety of the starch material used, with particular regard to its amylose:amylopectin ratio. It was of interest, therefore, to formulate mixtures of varying amylose:amylopectin ratios and determine the influence of additive incorporation and extrusion processing parameters on their behavior. To further explain the results observed during the process of extrusion, isothermal studies outside the extruder were conducted on the feed materials. Rates of gelatinization, as measured by DSC, X-ray crystallography and water absorption index; viscosity increase and changes in carbohydrate solubility were determined. Size exclusion chromatography was conducted to determine the degree of starch breakdown as affected by extrusion conditions and feed formulation.U of I OnlyETDs are only available to UIUC Users without author permissio