Ohmic heating of beef at 20 kHz and analysis of electrical conductivity at low and high frequencies

The increase in temperature during ohmic heating (OH) at 20 kHz of conventional beef (CB) and wagyuu beef (WB) was evaluated by analyzing the effects on drip loss due to cooking, shrinkage and microstructure changes. The effects of parallel and series current directions, temperature (5-65 °C), frequency (50 Hz-20 kHz), and chemical composition on the EC values of samples were evaluated. A mathematical explanation of the effect of current direction on EC was provided. A low drip loss due to cooking and shrinkage were found in both beef treated by OH at 20 kHz and 50 V. A good temperature uniformity independent of the current direction was obtained in CB. Increasing the frequency caused a drop in resistance and an increase in heating rate, thereby decreasing the heating time needed for beef muscles, especially for CB, due to its high water and low fat content. A large amount of endogenous fat in WB does not generate heat as quickly as CB muscles due to the poor conductivity of fat; therefore, the presence of fat decreases EC, resulting in uneven heating.