Rheological properties and microstructure characterization of normal and waxy corn starch dry heated with soy protein isolate

Physicochemical and microstructure properties of normal corn starch (CS) and waxy corn starch (WCS) with soy protein isolate (SPI) before and after dry heating were investigated by rapid visco analyser (RVA), rheometer, differential scanning calorimeter (DSC), x-ray diffraction (XRD), and scanning electron microscopy (SEM). Dry heating with SPI significantly increased the paste viscosities of both CS and WCS. Compared with untreated starch, the values of G' and G '' of all the samples significantly increased, and the tan d values decreased. The SEM images showed that starch accumulation occurred after dry heating with SPI, and WCS/SPI formed larger lump compared with CS/SPI. The starch accumulation suggested that the interactions between starch and SPI took place after dry heating starch/SPI mixture, and the interactions of WCS/SPI were more pronounced than those of CS/SPI. This simple heating process with SPI could be used as a promising modification method for WCS. (C) 2015 Elsevier Ltd. All rights reserved.