Shear-induced synergistic effects of konjac glucomannan and waxy potato starch on viscosity and gel strength

Abstract

Waxy potato starch (WPS) forms a highly viscous and elastic gel under a long-term low shear at a low temperature (24 h, 20 s−1, and 5 °C), and the gel elasticity and storage modulus (G′) increase with the addition of konjac glucomannan (KGM). In this study, a relatively short-term (10 h) of low shear (20 s−1) was applied to the WPS dispersion with the addition of three different KGMs. With a constant low shear, viscosities of KGM/WPS dispersions initially decreased (0–4 h) followed by an increase (4–10 h) back to the level of the initial viscosity. Shear-induced WPS gel formation was accelerated by addition of KGM. The G′ of KGM/WPS gel increased 25 times after shearing for 10 h and was 5 times higher than shear-induced WPS gel, which was caused by the formation of intermolecular double helices of WPS (melting ΔH ≈ 5 J/g; ΔG'(25-95°C)≈ 1100 Pa). Strong shear-induced synergistic effects with KGM and WPS were observed in the viscosity and G′, which was independent of the viscosity and elasticity of KGM dispersion.