Rheological characterization of schizophyllan aqueous solutions after denaturation-renaturation treatment.
Schizophyllan (SPG) with a molecular weight of 2.6x10(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 % <or= C(p) <or= 0.65 wt % and C(p) <or= 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*[eta] = 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.
Fang
Yapeng
Y
Department of Food and Human Health Sciences, Graduate School of Human Life Science, Osaka City University, Sumiyoshi, Osaka, 558-8585, Japan.
Takahashi
Rheo
R
Nishinari
Katsuyoshi
K
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D005782:Gels; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012212:Rheology / Q000379:methods; D012566:Sizofiran / Q000737:chemistry*; D012996:Solutions; D013314:Stress, Mechanical; D014783:Viscosity; D014867:Water
D005782:Gels; D012996:Solutions; D014867:Water; D012566:Sizofiran