Casein was modified by techniques like crosslinking with formaldehyde and grafting with monomers. Thermal stability of modified caseins was studied using viscosity and thermogravimetric analysis (TGA). Thermodynamic activation parameters were calculated from these results. Viscosity results suggest that there are transitions around 30 and 70 degrees C for casein grafted with acrylonitrile (AN) and n-Butyl methacrylate (n-BMA). DSC studies also show transition around 30 degrees C. DSC studies show that formaldehyde crosslinked casein irreversibly changes at around 120 degrees C.