Use of dielectric properties to detect whey protein denaturation

Denaturation of whey proteins can be detected by the dielectric properties. The dielectric properties of 20% whey protein with 0, 5 or 15% sugar, 2% salt, at pH 4 and isolated whey proteins were measured from room temperature to 100 degrees C at 300-2450 MHz. The temperature at which a decrease in the dielectric loss factor, or increase in the dielectric constant, occurred was compared to the temperature of denaturation as determined by DSC and found to match. The change in the dielectric properties is likely caused by binding of water and/or ions that occurs during protein denaturation. For most of the samples, the dielectric loss factor showed the protein denaturation, but when ions were present due to salt or low pH, the dielectric constant showed the denaturation.