Dielectric properties of β-lactoglobulin dispersions were measured at the selected microwave frequency range (915 and 2450MHz) by the open-ended coaxial probe method using a network analyzer. The effects of temperature (20–90°C), concentration (5–15% w/w) and pH (4–10) on dielectric properties were investigated using a response surface methodology and it was found to follow 2nd order polynomial models. Temperature and concentration significantly contributed on dielectric characteristics of β-lactoglobulin dispersion and pH of the dispersion exhibited the least effect. Dielectric parameters (ε′ and ε″) increased significantly at the close vicinity of denaturation temperature. Penetration depth (D p ) decreased with an increase in concentration and non-systematic with temperature.