Optimization and Energy Assessment of Carbon Dioxide Hydrate-Based Fruit Juice Concentration Process

Carbon dioxide hydrate-based technology is gaining popularity in the food industry as a potential alternative cold storage energy source in the juice concentration process. However, this technology has not been commercialized due to slow hydrate formation (inhibitory effect) and higher compression and refrigeration, which come with energy costs. Therefore, this study explored and optimized hydrate dissociation conditions and kinetic data from three (3) different juice systems to form carbon dioxide hydrates. Using a historical data design of response surface methodology (RSM) with surrogate models, optimal conditions and kinetic parameters were determined for the hydrate dissociations of bitter melon, grape, and pineapple juices. The RSM input variables include the system temperature (T = 274.15 to 276.15 K), juice concentration (Conc. = 88.5 to 97.4 wt.%) and pressure (P = 3.0 to 4.2 MPa), which were investigated on the responses of dehydration ratio (DHR) and apparent kinetic rate constant (K-app). Results obtained from the RSM analysis of variance (ANOVA) showed good correlation functions (R-2 > 0.9) of the responses, where the temperature was found as the most influential factor. At the optimal temperature of 275 K and pressure of 4 MPa, desirability efficiency of 99% bitter melon, 96% grape and 95% pineapple hydrate formation was achieved. This infers DHR of 80% bitter melon, 71% grape and 81% pineapple juice systems at K-app of 25, 19 and 21 mol G/mole-water.mins.Pa respectively. The energy required by each fruit juice conversion into a proposed hydrate formation process was estimated. Findings from this research could lead to the development of a technical support tool and a method for long-term juice concentration production analysis and process design.