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Vacuum Freeze Drying has a great impact upon the production of dehydrated food because of the superior quality of the product obtained. Whereas, due to the slow rate of vacuum freeze drying, the long operation cycle, the high energy consumption generated by the vacuum freeze drying machine at run time, the development of freeze drying food will be restricted. In order to find energy-efficient approaches and seek lower cost productions, investigation was made on the process of freeze-dried garlic slice production in the freeze-dried food factory. In this paper, through analyzing the basic principle and drying process of vacuum freeze-dried garlic slice, energy consumption of refrigerating system, heating system and vacuum pump system was studied. By asking technicians and production manager from the factory, the main processing technology was learned. In addition, according to the experiences and field investigation, the technical date of lyophilized system including compressor, evaporator, condenser, ammonia pump, drying chamber and industrial boiler was learned as well as the stable parameter during the actual production process. Based on the obtained datum, using the principle of refrigeration and appropriate date processing method, the energy consumption value was calculated and compared with other dry methods. The value of SMER (specific moisture extraction rate) is 0.32 kg/kW·h, and it costs 17.84 kW·h electric power per kilogram of products. Compared with hot-air drying system and heat pump drying system, the production process of vacuum freeze-drying system is very costly and energy intensive. In line with previous research and manufacturer's actual production situation, when the evaporation temperature increased from -35°C to -33°C, electric power of 400 kW·h was saved, and electric power of 48 kW·h was reduced by the changed pressure of drying chamber from 100 Pa to 130 Pa, meanwhile, the run time decreased from 23 h to 22 h. The results prove that energy can be saved by increasing appropriately the evaporation temperature and the pressure of drying chamber during the production of freeze-dried garlic slice. It can provide reference to practical operation. [ABSTRACT FROM AUTHOR]