Effect of extrusion treatment with different emulsifiers on the thermal stability and structure of corn starch

Abstract

Corn starch was treated with raw moisture (30%), screw speed (160 rpm), extrusion temperature (30, 55, 80, 105, 130, and 155° C), and emulsifier (1.2%) to produce the starch extrudate particles in a twin screw extruder. The influence of extrusion processing and composition (starch and emulsifier content) on the viscosity, microstructure, solubility, swellingpower, and thermal stability of starch extrudate particles was examined. The SEM results showed that the surface of starch extrudate particles was quite irregular and a fissure could be clearly observed. The X-ray intensities and relative crystallinity were decreased after extrusion treatment. The data highlighted that the gelatinisation temperature and solubility were increased and the gelatinisation enthalpy, viscosity, and swelling power were decreased. The emulsifiers present also influenced the thermal stability and solubility of starch extrudate particles, which were attributed to their ability to modify starch granule interactions. The thermogravimetric analysis and differential scanning calorimetry analysis indicated that the thermal stability of starch extrudate particles was improved after extrusion processing.