Optimal Technology of Freeze-Drying Process of Son-taroes

The technological characteristics of son-taroes of Colocasia esculenta Schott during freeze-drying process was studied, including the influence of the temperature decreasing rate, the vacuum, the temperature and heating programme of heating plate, and the temperature of condenser to the process and the product quality of freeze-drying taroes. The optimal technogical condition was: the temperature of freezing -30℃, the temperature of decreasing rate -0.2℃/min, the vacuum 66.7 Pa, the temperature of condenser -34℃～-40℃, the programme of heating plate was rising the temperature to 80℃ within 1.5 hours, keeping the temperature for 5 hours, then decreasing the temperature to 70℃ within 1 hour, keeping the temperature for 1 hour and then decreasing the temperature to 60℃ within 1 hour, at last, taking off the heater automatically, cooling the product to the room temperature naturally. The sensory quality of freeze-drying tatoes was obviously better than that of the products dried by the hot air. The restoration velocity in water was 34 times, the ability for restoration in water was 1.3 times, the contract rate of volume was 40.7% and the keeping rate of main nutrient α-VE of freeze-drying taroes was 2.15 times of that of the product dried by hot air.