Yield stress components of waxy corn starch-xanthan mixtures:Effect of xanthan concentration and different starches

摘要

Yield stress of 6% (w/w) waxy maize (WXM),cross-linked waxy maize (CLWM),and cold water swelling (CWS) starches in xanthan gum dispersions:0%,0.35%,0.50%,0.70%,and 1.0% was measured with the vane method at an apparent shear rate of 0.05 s~(-1).The intrinsic viscosity of the xanthan gum was determined to be:112.3 dL/g in distilled water at 25 deg C.Values of the static (sigma_(0s)) and dynamic (sigma_(0d)) yield stress of each dispersion were measured before and after breaking down its structure under continuous shear,respectively.The WXM and CWS starches exhibited synergistic behavior,whereas the CLWM starch showed antagonistic effect with xanthan gum.The difference (sigma_(0s) - sigma_(0d)) was the stress required to break the inter-particle bonding (sigma_b).The contributions of the viscous (sigma_v) and network (sigma_n) components were estimated from an energy balance model.In general,values of sigma_b of the starch-xanthan gum dispersions decreased and those of sigma_n increased with increase in xanthan gum concentration.