Experimental study and process parameters analysis on the vacuum cooling of iceberg lettuce

The vacuum cooling of iceberg lettuce was described in this paper. Based on the energy and mass balance, a mathematical model was developed to analyze the performance of the vacuum cooler and the evaporation–boiling phenomena during vacuum cooling of iceberg lettuce. The temporal trends of total system pressure, produce temperature such as surface temperature, center temperature, mass–average temperature, the weight loss of iceberg lettuce during vacuum cooling were predicted. Validation experimentation is achieved in the designed vacuum cooler. The experimental data were compared with the simulation results. It was found that the differences of the temperature between the simulation and the experiments were within 1 °C. The amount of water evaporated from the iceberg lettuce by simulation was 3.32% during the whole vacuum cooling, while the tested water loss rate was 2.97%, the maximal deviation of weight loss was within 0.59%. The simulation results agreed well with the experimental data.