Dielectric properties of β-lactoglobulin as influenced by pH, concentration and temperature

Dielectric properties of beta-lactoglobulin dispersions were measured at the selected microwave frequency range (915 and 2450 MHz) by the open-ended coaxial probe method using a network analyzer. The effects of temperature (20-90 degrees 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 beta-lactoglobulin dispersion and pH of the dispersion exhibited the least effect. Dielectric parameters (epsilon' and epsilon '') increased significantly at the close vicinity of denaturation temperature. Penetration depth (D-p) decreased with an increase in concentration and non-systematic with temperature. (C) 2009 Published by Elsevier Ltd.