Development of a PLC/IoT Control System with Real-Time Concentration Monitoring for the Osmotic Dehydration of Fruits

Osmotic dehydration (OD) is an effective pre-treatment for fruit preservation, but conventional processes often lack precision due to manual control of critical variables. This work reports the design and validation of an automated OD system integrating a programmable logic controller (PLC), human–machine interface (HMI), and IoT-enabled sensors for real-time monitoring of syrup concentration and process temperature. Mango (Mangifera indica) cubes were treated under a 23 factorial design with sucrose concentrations of 45 and 50 °Brix, immersion times of 120 and 180 min, and temperatures of 30 and 40 °C. Validation demonstrated that the IoT hydrometer achieved strong agreement with reference devices (R2 = 0.985, RMSE = 0.36 °Brix), while the PLC-integrated tank sensor also demonstrate improved performance over existing calibrated thermometer (R2 = 0.992, MAE = 0.20 °C). ANOVA indicated that concentration, temperature, and time significantly affected water loss and weight reduction (p 0.97). The findings highlight the effectiveness of the system for precise monitoring and optimization of OD processes.