| The materials used for the experiments were beef: fresh and frozen, fish: salmon, cod and ocean perch, egg: white and yolk, chicken: thighs and breast, and whey proteins: pH 6.25 and 4, with and without salt and sugar. The dielectric properties were measured from 10 to 115°C, at eleven different frequencies from 300 MHz to 2450 MHz.; The dielectric constant and loss factor both increased at the denaturation temperature for the collagen. When the sample was cooled and reheated again the change did not reoccur, indicating that the dielectric properties were measuring an irreversible change. As the frequency decreased the values of the dielectric constant and loss factor increased, and the changes in the dielectric properties at the denaturation temperature were larger.; When muscle protein denatures, it shrinks and expels water and minerals. The dielectric properties of the samples increased greatly at the denaturation temperature. Dielectric constant and loss factor, therefore, were elevated by denaturation of the proteins especially in beef, chicken, fish and egg yolk.; Whey proteins were also tested, with various additives. The dielectric loss factor of the 20% whey protein solution, decreased from room temperature to 40°C because of the effect of temperature on dilute salt solutions. When the temperature reached 65°C whey protein hydrophobic groups are exposed to the medium. The hydrophobic groups exposure greatly increased the order of the water. This increase in structure is reflected as an increase in the dielectric loss factor until 75°C. Further heating caused the complete denaturation of the whey protein between 75–80°C. When the protein denatured it exposed not only hydrophobic groups but also a significant number of dipoles. The whey protein at this stage will bind water and ions from the environment. This aggressive binding reduces the mobility of the water and causes a decrease in the dielectric loss factor.; Increasing sugar or salt content or decreasing the pH increases the denaturation temperature of the whey protein. This is detectable by dielectric property change. DSC results and dielectric change occurs at the same temperature. Protein denaturation, aggregation, unfolding and loss of the water bonding capacity of the hydrophobic groups can be observed with this method. |
