| Research was aimed at studying the optimum vacuum cooling process of cos lettuce precooled from initial core temperature of 19-21 °C to the final core temperature of 4±1 °C. The experiment was carried out in a rectangular vacuum chamber having a volume of 14.98 m3. In the experiment, the final pressures for vacuum-cooled cos lettuce were set at three different levels namely, 5.5, 6.0 and 6.5 millibar. The ressures were were at the final pressure of 0.60 kPa and the holding time of 25 minutes. The total cooling time was 39 minutes and the energy consumption was 4.17 kwh per 200 kilograms of cos lettuce. The electricity cost was 0.067 baht per kilogram of fresh weight. The weight loss during precooled cos lettuce with the previous optimum parameters was... |
