Molecular weight effects on gelation and rheological properties of konjac glucomannan–xanthan mixtures

Abstract

AbstractFractions of konjac glucomannan (KGM) with various viscosity‐average molecular weights (Mv) ranging from 4.00 × 105 to 2.50 × 106 were prepared by hydrolysis degradation in hydrochloride acid/ethanol. Effect of Mv of KGM on the critical gelation temperature (Tgel) determined by Winter–Chambon criterion and the elasticity of KGM/xanthan mixed gels, a kind of binary gel formed by synergistic gelation, were investigated by dynamic viscoelastic measurements. It was shown that the value of Tgel of the gel was shifted to a higher temperature and the gel strength was enhanced when Mv of KGM was increased. The critical Mv (1.91 × 106) was observed, above which the Tgel and elasticity of the mixed gels showed no or slight increase. It was suggested that Tgel and elasticity of KGM/xanthan mixed gels mainly depend on the structure of junction zones driven by the strong interaction between KGM and xanthan, which was gradually improved with increasing Mv of KGM. It was found that the critical strain and yield stress of the mixed gels increased monotonically with the increasing Mv of KGM. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 313–321, 2010