|Budget Amount *help
¥3,100,000 (Direct Cost : ¥3,100,000)
Fiscal Year 1998 : ¥1,200,000 (Direct Cost : ¥1,200,000)
Fiscal Year 1997 : ¥1,900,000 (Direct Cost : ¥1,900,000)
The fractal structure of aggregates in heat-induced BSA and beta-lactoglobulin gels prepared with and without CaCl_2 was examined. From the concentration dependence of the gel elasticity determined from a uniaxial compression test of the gel, the fractal dimensions D_f of the aggregates in the gels were evaluated, using the theory of Shih et al.. It was confirmed that the gels with and without CaCl_2 showed weak-and strong-link behavior in the theory of Shih et al., respectively. The obtained values of D_f were about 2 for strong-link gels and about 2.7 for weal-link gels. In addition, as for the beta-lactoglobulin gels containing CaCl_2 (weak-link type), from the analysis of the gel image obtained with confocal scanning laser microscopy of the gels, the fractal dimensions were also evaluated, the value being close to that evaluated from the gel elasticity measurements. These results indicate that the elastic behavior of the aggregate gels is a reflection of fractal structure of the ag
gregates in the gels.
The fractal dimension D_f of aggregates in dilute BSA system with salt addition was evaluated by static light scattering (SLS). The fractal structure was observed for the system with NaCl addition. The values of D_f increased with increasing beating time and ionic strength. The values of D_f were larger than those (D_f=1.8 or 2.1) predicted by the conventional cluster-cluster aggregation model, probably due to "restructuring" of aggregates during aggregation process. On the other hand, the fractal structure was not observed for the system with CaCl_2 addition.
The dielectric properties of a typical ionic food polysaccharide, kappa-carrageenan, were investigated with special relevance to the sol-gel transition of its dispersed system. The dielectric relaxation around 1 MHz due to counterions bound to the polyelectrolyte was analyzed. For the disordered (coil) state of kappa-carrageenan solutions, dependence of the dielectric increment, EPSILONepsilon and that of the relaxation time, tau, on the polymer concentration, C, were summarized as EPSILONepsilon^<oc> C^0 and tau^<oc> C^<-1>, respectively, in good agreement with the scaling relations for the semi-dilute solutions derived from the polyelectrolyte solution theories. For the ordered (helix) state of kappa-carrageenan dispersed systems, the values of the dielectric parameters, DELTAepsilon and tau, were larger than the predicted values using the scaling equations for the semi-dilute solutions. The deviation between the measured and predicted values can be understood as a result of the association of the helical conformers in gels.