Addition of native konjac to skim milk caused phase separation at levels of 0.03% w/w. However, high shear modification of the konjac reduced the molecular weight of the polysaccharide, which altered its thermodynamic behaviour in the presence of protein, thus allowing it to be added to skim milk as a viscosity-enhancing agent without the occurrence of macroscopic phase separation. Addition of modified konjac increased the stability to sedimentation of UHT-treated skim milk during simulated storage, without significantly affecting either the colour or particle size post heat treatment. In conclusion, addition of mechanically modified (low molar mass) konjac could provide a mechanism to enhance both the viscosity and stability of colloidal protein preparations at concentrations more suitable for processing, compared to native konjac.