Linear and Nonlinear Rheology of Mixed Polysaccharide Gels. Pt. I. Young's Modulus, Ring Extension and Uniaxial Compression Tests.

Abstract

Small and large deformation tests were performed on polysaccharide-based gels containing konjac glucomannan, locust bean gum and κ-carrageenan. Low pH degradation of κ-carrageenan during heating led to lower gel strength. When κ-carrageenan degradation was avoided, the linear-regime rheology was dominated by the κ-carrageenan content, and the storage Young's modulus (E') was found to decrease with decreasing κ-carrageenan concentration. The large deformation behavior, however, was dominated by the konjac glucomannan concentration, and the rupture strain increased strongly with increasing konjac concentration. These two opposing trends led to a maximum in rupture stress in extension tests. No rupture was observed in compression of the gels at the polysaccharide concentrations tested. The compression force of konjac-rich gels was lower than that observed for gels without konjac at low-compression degrees, but it was similar to or higher at high-compression degrees, above 60-80%, indicating the higher degree of strain hardening of konjac-rich gels. PRACTICAL APPLICATIONS: Mixing of different polysaccharides has been used for widening the texture range, and it was shown in this report that the mixture of konjac glucomannan, locust bean gum and κ-carrageenan in the presence of sucrose and acid can produce jellies with various textures.