Molecular origin for the thermal stability of Koshihikari rice amylopectin

• Published in: Food research international Vol. 33; no. 1; pp. 35 - 40
• Main Authors: Tako, Masakuni, Hizukuri, Susumu
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2000
• Subjects: amylopectin; aqueous solutions; dimethyl sulfoxide; hydrogen; Intramolecular associations; Rheology; rice; Rice amylopectin; sodium hydroxide; temperature; Thermal stability; urea; van der Waals forces; viscoelasticity; viscosity; Intramolecular associations; Rice amylopectin; Rheology; Thermal stability
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/S0963-9969(00)00021-1

The non-Newtonian behavior and dynamic viscoelasticity of Koshihikari rice amylopectin (waxy type) in aqueous solution were investigated. The flow curves, at 25°C, of Koshihikari amylopectin showed plastic behavior at various concentrations. The viscosity increased slightly with increase in temperature up to 25°C, then it decreased a little with further increase in the temperature at a concentration of 6%. The dynamic modulus showed very large values and stayed constant during increase in temperature at 2.0 and 4.0%, but a little increase of dynamic modulus was observed at 6.0% solution. The dynamic modulus decreased slightly upon addition of urea (4.0 M) or 85% DMSO and decreased gradually with increase in the temperature. The dynamic modulus, however, was lower in 0.10 M NaOH solution than in aqueous solution and decreased rapidly when the temperature reached 45°C, which was estimated to be a transition temperature. The results obtained support the mode of intramolecular associations within rice amylopectin molecules previously proposed. An anomeric hydrogen atom may take part in an intramolecular van der Waals forces of attraction with an adjacent OH-6 or methylene group of d-glucosyl residue.