Circuit-theory prediction of thermal gradients in yield-stress multiphase food systems during ohmic heating

Ohmic heating (OH) enables rapid and uniform volumetric heating but remains challenging to model in heterogeneous food systems containing yield-stress matrices. This study proposes and validates, at bench scale, a simplified lumped circuit-analogy model to predict temperature evolution in a static multiphase configuration composed of potato puree (viscoplastic, non-convective) containing meatball inclusions. While CFD/FEM-based frameworks can provide detailed electro-thermal field resolution, their computational cost limits real-time or iterative process optimization. The proposed circuit-analogy model offers a rapid and physically consistent alternative for preliminary design and predictive analysis. The model was validated experimentally under different conductivity ratios and particle configurations using a 50 Hz, 40 V ohmic heating system. Conductivity matching reduced temperature gradients from 30–39 °C to 6–15 °C by eliminating electric-field shadowing that otherwise reduced local heating rates by ≈17%. The model reproduced puree temperatures with RMSE < 2 °C and, in the asymmetric configuration, conservatively under-predicted meatball core temperatures by up to ~10 °C at the end of treatment, while remaining robust to plausible variability in key thermophysical properties (electrical conductivity and volumetric heat capacity). Predictive scale-up simulations in a scaled-up chamber (19.6 × 10.6 × 12 cm; eight inclusions; 120 V), for which no pilot-scale experimental verification was performed, indicated improved heating uniformity (ΔT ≤ 6 °C) and attainment of the target core temperature for lethality (74 °C) without puree over-processing under the idealized inclusion arrangement considered. These results demonstrate that conductivity mismatch is the dominant driver of non-uniform OH in viscous, non-convective foods. Overall, the circuit-based framework provides a rapid, physically grounded, and computationally efficient tool to support preliminary process design and conservative safety assessment in multicomponent ready-to-eat systems. • A solid-like continuous phase limits bulk convection in multiphase foods. • A lumped‑element circuit framework captures conduction‑dominated heating. • Conductivity mismatch drives non‑uniform heating in heterogeneous foods. • Solid-inclusion arrangement modulates current focusing and heating uniformity.