Assessment of gelation behaviour of fenugreek gum and other galactomannans by dynamic viscoelasticity, fractal analysis and temperature cycle

Abstract

Gelling properties of three galactomannan dispersions (fenugreek (FG), guar (GG) and locust bean gum (LBG)) were compared by strain and frequency sweep viscoelasticity, and temperature cycle at a constant strain and frequency in the concentration range 1 to 2 wt%. For FG and GG dispersions, tan δ remain <1 in the linear viscoelastic region during strain sweep analysis. FG and GG dispersions also showed a sol to gel transition at higher frequencies compared to LBG, indicating gelation by inter-polymer interactions and network formation. Conversely, strain and frequency sweep analysis of LBG dispersions revealed poor gelling ability. The fractal dimensions of the gels were 1.82, 2.38 for FG and 1.64, 2.10 for GG, using Shih (1990) and Wu-Morbidelli model (2001), respectively. According to the Shih model, FG and GG fell into the strong gel regime, but the Wu-Morbidelli model revealed that both dispersions were in the transition gel regime, more inclined towards weak gels, which is a more accurate description of the gels. FG and GG could form thermo-reversible gels, while for LBG, an improvement in gel strength was observed after the temperature cycle. The dynamic viscoelastic studies on FG dispersions support their use as food gelling agents.