Chemical and processing aspects of the production of cationic starch using extrusion cooking.

Cationic potato starches were produced by carrying out the chemical reaction under varying extrusion cooking conditions in order to investigate the influence of the extrusion parameters on the reaction efficiency (R.E.) and the degree of substitution (D.S.) dependent on this. The extrudates were used to develop a suitable analytical method for an accurate determination of the D.S. To achieve the necessary analytical accuracy all nitrogen containing substances not chemically bound to the molecules of the starch must quantitatively be extracted from the cationic starch prior to the determination of its nitrogen content. It could be shown by extraction experiments that the extractability of such substances from ground cationic potato starch extrudates is dependent on the penetration of the solvent through the extrudate particles and the diffusion of the soluble substances in the particles into the solvent. Optimal results for the R.E. were achieved by suspending one part ground cationic potato starch extrudate in ten parts solvent consisting of 80% Ethanol and 20% water (w/w). The suspension had to be kept in a sealed glass vessel for 40 min at a temperature of 80 degrees C. Within the experimental range of the extrusion experiments the reaction conditions for the cationization could be kept constant. Besides the formulation of the reactive components the D.S. was influenced by the variation of the extrusion parameters. A R.E. of 80% was achieved over the investigated range for the D.S. of 0.03 to 0.10.