PRODUCTION OF STARCH DERIVATIVES BY COOKING EXTRUSION

It was possible to produce starch derivatives from corn and potato starches and maize grit by cooking extrusion process with a conical, counter-rotating twin-screw extruder. The used chemical reagents for derivatization were citric acid for citrate-starches, sodium trimetaphosphate for phosphate-starches and 2,3-epoxypropyltrimethyl-ammonium chloride and 3-chloro-2-hydroxypropyl trimethyl-ammonium chloride for cationic starches. With citrate starches 60-70% of bound citric acid yields were found in the extrudates. Heat treatment of extrudates after extrusion increased the amount of bound citric acid to 68-77% and icreased Brabender-viscosity values. Shear stability and freeze-thaw stability were also improved. For phosphate starches 15-30% of bound phosphate were found in the extrudates. After heat treatment bound phosphate was increased to 20-35%. Physical and functional properties were also improved. The production of cationic starches by cooking extrusion process was also possible. There was about 50-60% of bound nitrogen from reagents in the extrudates. This yield was further increased to 65-90% after heat treatment.