Multivariate study of process parameters for thermal processing of watermelon juice in a double pipe heat exchanger with phase change material

Erythritol, a heat-stable natural sugar substitute, is extensively used as a phase change material (PCM) to enhance heat transfer efficiency and prevent thermal degradation of food. This study aims to give thermal treatment on watermelon juice using an erythritol and water mixture in a double-pipe heat exchanger in place of base fluid. The thermal processing parameters were varied as: temperature of hot liquid (85, 90 and 95 °C), holding time (20, 40 and 60 sec) and PCM concentration (0, 1.5 and 3%). The multivariate analysis and optimization using RSM with BBD model were carried out to evaluate the impact on lycopene retention (LC), ascorbic acid retention (AA), color difference (ΔE*), TPC, TSS, and pH. The LC and AA retention increased to 92.3% and 68.12%, respectively, with 3% PCM concentration at 85 °C for 20 seconds. However, pH, TPC, and TSS did not change significantly with an increase in the PCM concentration. In Pearson’s correlation matrix, nutritional compounds (TPC, LC, AA) showed strong negative correlations with hot fluid temperature (r=-0.72 to-0.75, p≤0.01) and ΔE* (r=-0.84 to-0.89, p≤0.01). PCA explained about 75.18% of variability (PC1: 55.42%, PC2: 19.76%). The optimal thermal processing conditions for watermelon juice were found at 85.79 °C, 20s holding time, and 3% PCM that yield lycopene retention of 71.11 mg/kg, ascorbic acid 5.41 mg/100ml, TSS of 9.2°Brix, and TPC of 10.7 mg GAE/ml. This study highlights the promising potential of PCM in nutrient retention and color preservation during the thermal processing of watermelon juice.