Effects of reactive extrusion on cross-linking of corn starch

The present work aimed to evaluate the efficiency of the dual modification of corn starch by reactive extrusion, using a mono-thread extruder, and also sodium tripolyphosphate and trimetaphosphate to obtain cross-linked starch. Native starch, extruded native starch, and starch cross-linked by conventional methods were used as standards to evaluate the modification efficacy by reactive extrusion. The content of phosphorus residues allowed by legislation in starch modification is 0.4%. Therefore, the reactive extrusion demonstrated greater effectiveness because cross-linked starch obtained by this method was within the established limit of phosphorus residues, in contrast to that obtained by the conventional method, which exceeded this amount. In addition, it required greater water consumption for residual removal, therefore producing effluents, and also wasting energy and time. Cross-linking by the extrusion process showed a profound influence on the characteristics of modified starch, generating specific functional characteristics, mainly in terms of pasting properties. Also, the samples presented low viscosity and pasting temperature. In conclusion, cross-linking through reactive extrusion was fast, produced starch with phosphorus content within the limits allowed by legislation, and generated different physicochemical characteristics.