Abstract
The flow behavior, dynamic viscoelasticity, and optical rotation of aqueous solutions of wheat amylose were measured using a rheogoniometer and a polarimeter. The amylose solutions, at 25 °C, showed shear-thinning behavior at a concentration of 1.2%, but plastic behavior at 1.4 and 1.6%, the yield values of which were estimated to be 0.6 and 1.0 Pa, respectively. The viscosity of the wheat amylose increased a little with increase in temperature up to 10 or 20 °C at 1.2% or 1.4 and 1.6%, which was estimated to be a transition temperature. The elastic modulus increased with increase in concentration, and increased with increasing temperature up to 20, 25 and 30 °C, which was estimated to be a transition temperature, respectively, then decreased gradually but stayed at a large value even at high temperature (80 °C). A very low elastic modulus of the wheat amylose was observed upon addition of urea (4.0 m) and in alkaline solution (0.05 m NaOH) even at low temperature. The optical rotation of wheat amylose solution increased a little with decreasing temperature down to 25 °C, then increased rapidly with further decrease in the temperature. The mode of gelation mechanism of amylose molecules, which was previously proposed, was confirmed and a retrogradation mechanism of wheat amylose was proposed.
Highlights
Starch is a major component of many food plants and is used in food, cosmetics, paper, textile, and some other industries as thickening, stabilizing, or gelling agents
Under steady angular force, both intra- and intermolecular hydrogen bondings of amylose molecules are stable until the temperature reached 65–80 °C. This model corresponds to a double-stranded helix, a single helix seems to exist in part with the formation of side-by-side intermolecular hydrogen bondings in aqueous solution where C-3 of OH groups of D-glucosyl residues take part in the interaction
Transition temperature at which viscosity decreased rapidly was observed in aqueous solutions of wheat amylose at 20 °C, but it retained a large value even at 65–70 °C, which was estimated to be secondary transition temperatures
Summary
Starch is a major component of many food plants and is used in food, cosmetics, paper, textile, and some other industries as thickening, stabilizing, or gelling (pasting) agents. Starch consists of two polymers, amylose and amylopectin, the molar ratio of which is about 20–30% and 80–70%, respectively. Amylose is a linear polysaccharide composed of 1,4-linked α-D-glucosyl residues by definition, but the actual specimens, which are isolated and purified from starches, include slightly branched molecules [1,2,3]. Amylose produces a gel by cooling after heating aqueous suspension at high temperature range (120–140 °C). We have proposed a possible gelation mechanism of potato amylose in aqueous solutions [4]. An intramolecular hydrogen bonding takes place between OH-6 and the adjacent hemiacetal oxygen atom of the D-glucopyranosyl residues, as illustrated in Scheme 1. Intermolecular hydrogen bonding takes place between OH-2 and the adjacent O-6 of the
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
