Freeze-drying technology removes almost 100% of water from food products by performing the drying process of frozen food under vacuum conditions, causing ice to sublimate directly into vapour. The final products are high-quality, flavourful products that can be stored at room temperature for a long time. Conventional freeze-drying is time-consuming, mainly due to the diffusion of moisture out of the food products. To speed up the process, freeze-drying can be integrated with the vacuum-freezing technique. This innovative cooling and freezing method is based on heat removal utilizing the evaporation heat induced by lowering the pressure in the chamber. Vacuum freezing is a rapid freezing method that enhances the porosity of foods, which, as a result, reduces their drying time.
The “Long-term food storage” demonstrator integrates a modern freeze-dryer with a vacuum freezing system for domestic small-scale application. Numerical simulations of the process will improve the control system and shorten the total drying time of foods. This technology reduces food waste, enables storage and transport without chilling or freezing, and therefore lowers energy demand and GHG emissions.
The FrostX vacuum-freezing aided freeze-dryer operates in both standard and vacuum-freezing modes. Initial tests compared cooling times between both modes, showing a significantly higher cooling rate in the vacuum-freezing mode. Energy consumption was measured for both scenarios, revealing a 38% reduction in energy usage with vacuum-freezing for a 3 kg load. These results will help optimize the demonstrator’s controller for further energy reduction. Future experiments at Silesian University of Technology and FrostX will use larger and mixed food loads, reflecting potential end-user applications, and at the same time, monitoring wear and tear on key system components for maintenance recommendations.
Vacuum freeze-drying chamber during the ongoing process (right) and dried products (left)
