INFLUENCE OF EXTRUSION-COOKING CONDITIONS ON THE EFFICIENCY OF THE CATIONIZATION AND CARBOXYMETHYLATION OF POTATO STARCH GRANULES

A systems analytical model for the extrusion of starches and flours wa s modified to determine the optimal extrusion conditions for the catio nization and the carboxymethylation of potato starch and to determine the effect of the extrusion conditions, optimal for the reaction yield (R.E.) and the desired degree of substitution (D.S.), on the theologi cal properties of the derivatives. In order to improve the describabil ity of the postulated functional relationships between the defined sys tem parameters and the R.E. it was decided to measure the heat flow ov er the length of the processing part of the extruder in order to enabl e a more precise measure of the specific thermal energy input (STE). T est run results showed that the STE is highly correlated to the SME. T herefore the initial proposal to substitute the STE for the product te mperature in the modified systems analytical model could not be succes sful. The extension of the working range for these trials to higher SM E and mean residence time levels compared to previous studies enabled the production of cationic starch with a maximum R.E.>90% and the prod uction of carboxymethylstarch with a maximum R.E. of about 85%. The mo dified systems analytical model could not yet be used precisely for th e optimization of the R.E. of the derivation of starches. The influenc e of process parameters and D.S. on theological properties of the exam ined derivatives could be described with regression equations.