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

Abstract Fractions of konjac glucomannan (KGM) with various viscosity‐average molecular weights ( M v ) ranging from 4.00 × 10 5 to 2.50 × 10 6 were prepared by hydrolysis degradation in hydrochloride acid/ethanol. Effect of M v of KGM on the critical gelation temperature ( T gel ) 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 T gel of the gel was shifted to a higher temperature and the gel strength was enhanced when M v of KGM was increased. The critical M v (1.91 × 10 6 ) was observed, above which the T gel and elasticity of the mixed gels showed no or slight increase. It was suggested that T gel 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 M v of KGM. It was found that the critical strain and yield stress of the mixed gels increased monotonically with the increasing M v of KGM. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 313–321, 2010