Effect of melt-processing and ultrasonic treatment on physical properties of high-amylose maize starch.
High-amylose maize starch (Hylon VII) was submitted to melt-processing in an internal mixer at 100 degrees 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 at 5 g/L, and treated by ultrasound radiation at the same conditions for 30 min. Samples were characterised by (1)H 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 (1)H 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.
Universidade Federal do Rio de Janeiro, Instituto de Macromoléculas Professora Eloisa Mano, Centro de Tecnologia, Bloco J, PO Box 68525, 21945-970 Rio de Janeiro, Brazil.
Felipe F
FF
Lima
Cristina T
CT
Andrade
D000688:Amylose / Q000737:chemistry*; D005990:Glycerol / Q000737:chemistry; D044367:Phase Transition; D011522:Protons; D013696:Temperature; D014465:Ultrasonics; D014783:Viscosity; D014961:X-Ray Diffraction; D003313:Zea mays / Q000737:chemistry*
D011522:Protons; D000688:Amylose; D005990:Glycerol