Effects of operation processes and conditions on enhancing performances of vacuum cooling of foods: A review

Background: Vacuum cooling (VC) is a cooling technology for moist and porous foodstuffs with superiority in cooling rate, uniformity and hygiene, and low energy consumption. However, there are still some disadvantages that weaken the competitiveness of industrial applications such as the inevitable mass loss and uneven cooling in different parts of leafy vegetables. In order to improve the performance of VC, many efforts have been performed. Scope and approach: In this review, the basic information of VC and the main applications for fruit, vegetables and meat products as well as limitations are described first. Improvements for enhancing performances of this technology in terms of operation processes including pre-treatment, technical optimization and integration, as well as equipment upgrade, and optimized operation conditions such as final pressure and pressure reduction rate are discussed. In addition, the limitation and further prospects of VC in the food industry are also mentioned. Key findings and conclusions: The findings presented in this review demonstrated that optimizing operation processes and controlling operation conditions can effectively improve the performance of VC including mass loss, cooling rate and energy consumption and temperature distribution. However, many enhancing strategies still have limitation for applied in the food industry. Future trends of VC are the study of moisture migration characteristics based on food microstructure and multi-functional optimization of VC process or system. It is hoped that the current review can provide some guidance for further developments of the VC technology.