Effect of melt-processing and ultrasonic treatment on physical properties of high-amylose maize starch

High-amylose maize starch (Nylon VII) was submitted to melt-processing in an internal mixer at 100 C and 40 rpm for 8 min Glycerol was used as a plasticiser at different polymer/glycerol ratios Torque and temperature curves were obtained After glycerol extraction with ethyl alcohol, the samples were dispersed al 5 g/L, and treated by ultrasound radiation at the same conditions for 30 nun Samples were characterised by H-1 NMR spectrometry, viscosity measurements, and X-ray diffractometry. The results revealed that both glycerol and water had an important role on the crystallinity properties of the resulting products Melt-processed and sonicated samples showed similar H-1 NMR spectra. Ultrasound treatment caused a significant reduction in intrinsic viscosity for the sample previously processed with the highest glycerol content, probably because of its higher solubility in water. (C) 2010 Elsevier B.V. All rights reserved.