Effect of Extrusion Cooking on Molecular Parameters of Corn Starch

Abstract

By using a systems analytical model (SAM) and a fuzzy logic control software (fuzzy CIM) extrusion experiments were designed, that enabled a differentiation of the influence of the thermal energy input, expressed by the product temperature (PT), and the influence of the specific mechanical energy input (SME) on the molecular structure of extruded starch. The chromatographic examination of the molecular changes in the starch clearly revealed the influence of the extrusion cooking conditions on molecular degradation.The molecular size of extruded starch, expressed as the weight average of the molecular weight (M __ w ), decreased exponentially when SME increased. In the range of 110-180 °C, PT had no significant influence on M __ w so that the observed reduction of M __ w was primarily dependent on the increase in SME. By contrast, the polydispersity depended both on PT and SME. The influence of PT on the polydispersity was of minor significance up to 160 °C, increasing more steeply at higher temperatures. PT increase above 180 °C resulted in increasing reducing power of the extruded starch, whereas SME had almost no effect on reducing power. Only at a PT of more than 180 °C small amounts of short chain molecules with a degree of polymerisation (DP) smaller than 6 could be determined.

Description of Extrudate Characteristics in Relation to the Shear Stress of Plasticised Starches Determined In-line

“…The same results were obtained for mixtures consisting of equal parts of two of the starches being studied [2]. The differences in the functional properties of the extrudates can only result from differences in the molecular structure of the extrudates, including the size of the amylopectin molecules [18].…”

Analysis of the dispersive mixing efficiency in a twin-screw extrusion processing of starch based matrix

“…Furthermore, it can be seen that increasing screw speed led to decrease in viscosity. This happens due to higher mechanical energy input at higher screw speeds leading to more intensive degradation of the starch which eventually results in lower matrix viscosity (Brümmer et al, 2002;Lai and Kokini, 1991;van den Einde et al, 2004).…”

Process, structure and texture of extruded whole wheat

“…This increase is mostly due to the release of soluble amylose and degradation of amylopectin branches (e.g. Brümmer et al, 2002). The main effect of the process conditions on the sample properties is shown in Fig.…”