Modeling the Effects of Temperature and Total Soluble Solids on Electrical Conductivity of Passion Fruit Juice During Ohmic Heating

This study models the electrical conductivity (EC) of passion fruit juice during ohmic heating under voltage gradients of 10, 20, and 30 V/cm, considering temperature (25–85 °C) and total soluble solids (TSS: 11.5, 15.5, and 19.5 °Brix). EC was measured using a laboratory-scale ohmic heating system, and three empirical models were developed using non-linear regression with the Levenberg–Marquardt algorithm. The second-order polynomial model showed the highest accuracy (R2 = 0.9974; RMSE = 0.0191; χ2 = 0.0112). EC increased with temperature, which enhanced ion mobility and decreased viscosity, while its relationship with TSS was non-linear: EC rose at low to moderate TSS but declined at higher concentrations, attributed to reduced free water and ion solute interactions. The validated model offers a reliable tool for real-time process control in industrial scale pasteurization and evaporation of tropical fruit juices.