Equivalent similarity numbers determination for describing the heat conduction process of meat products during baking

The process of heating meat products during their baking can be described based on the application of the theory of non-stationary thermal conductivity. However, when determining the Fourier and Biot similarity numbers, the problem of taking into account the variability of the thermophysical characteristics (TPC) of biological material arises. The change in the thermal and physical characteristics of meat products during heating occurs according to complex laws, which is caused by the thermal effects of phase and physicochemical changes. Based on the theoretical studies, a method for determining the equivalent Fourier and Biot numbers is proposed, taking into account the combined change in the thermal and physical characteristics of the surface and internal layers of meat products during baking. The authors conducted experimental studies to evaluate the effectiveness of the proposed method. Samples of minced meat with different fat-to-moisture content ratios (wet skimmed and low-moisture fatty) were selected as objects of study. The samples were formed in the form of bodies of canonical shapes – one-dimensional plates and cylinders. Heat treatment was carried out in a convection apparatus with direct contact of the product with heated air, which was achieved by using rod cassettes. Equivalent values of thermal conductivity were calculated for the selected materials. The results of the experimental studies were presented in the form of graphical dependencies Θ = f (Fo) using equivalent and variable values of thermophysical characteristics on temperature. The obtained curves form practically straight lines for both variants of accounting for TPC, characteristic of the regular mode of non-stationary thermal conductivity. Comparison of the data shows that when using equivalent values of the TPC, the convergence of the experimental points is higher than when using variable values of the TPC.