This study examines the impact of temperature and total soluble solids (TSS) on electrical conductivity (EC) of passion fruit juice during ohmic heating to establish predictive mathematical models. Experiments were carried out on juice samples with a TSS of 11.5, 15.5, and 19.5 °Brix, exposed to voltage gradients of 10, 20, and 30 V/cm, and heated from 25°C to 85°C. The results indicated that EC increased with temperature and was nonlinearly related to TSS. High TSS increased conductivity at first, but excess TSS decreased EC due to higher viscosity, less free water, and ion-sugar interactions. Linear and nonlinear regression models were tested for predicting EC. A second-order polynomial model that included temperature, TSS, and their interaction terms exhibited the highest accuracy, with R² values as high as 0.9974, coupled with low RMSE and χ² values. The research validates ohmic heating as a means of electrical conductivity behavior determination in fruit juices and provides a model that has been validated to enable process optimization and control in passion fruit juice thermal processing and vacuum evaporation. The model serves as a tool for real-time process control and can be applied to industrial-scale ohmic heating systems in tropical fruit juice processing.
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Assawarachan et al. (2025) studied this question.