One-Dimensional Transient Model of Food Product Temperature and Weight Loss Evolution in a Vacuum Cooler With Membrane Humidification

Abstract

A one-dimensional, transient model was developed to predict the temperature and weight loss evolution of a food product cooled using a vacuum cooling system with membrane humidification. The model included the following: (1) a sub-model based on the mass conservation of air and vapor inside the vacuum chamber; (2) a sub-model based on the coupled mass and heat transfer with inner vapor and heat generation; and (3) a sub-model based on the mass conservation of water vapor along the flow channels inside the humidifier. The vacuum chamber pressure was reduced from 1 atm to 2200 Pa using a vacuum pump with deflating speed of 500 m3/hr and condenser and membrane humidifier operating temperatures of 13°C and 60°C, respectively. A meat joint with a weight of 5.30 kg was cooled from an initial core temperature of 74°C to below 10°C. The conventional and modified models both cooled the food product to 10°C in 25 minutes. It was found out that increasing the chamber relative humidity reduced the surface water evaporation while the internal evaporation rate remained the same. Thus, the meat's moisture content, which was initially at 73.51%, was reduced to only 65.44%-an improvement from the conventional vacuum cooling system's 64.31%. This translated to product weight loss of only 10.98%, which represented significant progress compared to the conventional system's 12.51%. The simulation results indicated that employing humidification in a vacuum cooling system reduces the product total moisture loss while maintaining the rapid cooling rate.