Rheological characterization of schizophyllan aqueous solutions after denaturation–renaturation treatment
✍ Scribed by Yapeng Fang; Rheo Takahashi; Katsuyoshi Nishinari
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2004
- Tongue
- English
- Weight
- 201 KB
- Volume
- 74
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
Schizophyllan (SPG) with a molecular weight of 2.6×10^6^, designated SPG‐1, is denatured and then renatured at a concentration of 1.8 wt % by alkalization–neutralization. The prepared denatured–renatured samples (DRSPG‐1) are diluted to various concentrations and equilibrated for 10 days before rheological and intrinsic viscosity measurements. When concentration (C~p~) is above 0.75 wt %, DRSPG‐1 aqueous systems have weak gel‐type rheological properties. However, for 0.28 wt % ≤ C~p~ ≤ 0.65 wt % and C~p~ ≤ 0.19 wt %, DRSPG‐1 aqueous systems behave as power law fluids and Newtonian fluids, respectively, which are attributed to the moderate isotropy degree of DRSPG‐1 chains. Furthermore, a critical overlap parameter of c*[η] = 1.2 is determined for DRSPG‐1 in aqueous solutions, which is close to that of 1 for intact SPG in water while far smaller than that of 4.3 for SPG in DMSO. This is considered to be due to the strong interactions of DRSPG‐1 chains in water, further confirmed by the intrinsic viscosity measurements in which the DRSPG‐1 aqueous solution shows an abnormally large value of Huggins constant. Regarding the structure of DRSPG‐1 weak gels, multiruns of dynamic strain sweep measurements suggest that the dominant structures are aggregates formed by hydrogen‐bonding associations of DRSPG‐1 chains rather than the permanent three‐dimensional network. In addition, the step‐shear rate tests are performed to study the thixotropic properties of DRSPG‐1 aqueous systems. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004