Effect of Food Eutectic Point and Co-melting Point on Energy Consumption of Food Freeze Dryer
The eutectic point and eutectic point of food are important physical parameters to be considered in vacuum freeze-drying. It directly affects the quality of freeze-dried food. Therefore, before starting the food freeze-drying process, it is necessary to first understand the eutectic point and inclusive point of the food. Then, formulate reasonable process parameters for food material freezing, improve the quality of freeze-dried food, shorten freeze-drying time, and reduce energy consumption and cost of freeze-drying machine.
1, the eutectic point of food
The eutectic point of food refers to the temperature of the material when the moisture in the food material is completely frozen. Before the food is freeze-dried, the material needs to be pre-frozen. If the freezing temperature of the material is too low, the freeze-drying time will be prolonged and wasteful. Energy; if the freezing temperature is set too high, the material is not completely frozen, the material will cause partial boiling and foaming in the biochemical process, and the moisture removal of the food cannot be ensured, resulting in deformation, softening or even disintegration, resulting in lyophilization. The product is hardened and the quality of the product is degraded. Therefore, the pre-freezing temperature of the vacuum freeze-drying process should be set according to the eutectic point of the material. In order to ensure the complete freezing of the food, the pre-freezing temperature of the food material is generally controlled to be 5 to 10 ° C lower than the eutectic point.
2. The point of integration of food
The eutectic point of a food is the temperature at which the food that has been completely frozen into ice rises as the temperature of the ice crystal begins to melt. The eutectic point and eutectic point of food are two opposite processes, but the two temperatures do not coincide. The eutectic point of the same food material is lower than the eutectic point. This is because the eutectic point is all frozen in the food. The temperature at which the eutectic point is the temperature at which the already frozen material begins to melt. Generally, when the food material is dried, the heating temperature cannot be higher than the co-melting point temperature of the material. Otherwise, bubbles will be generated inside the material, and melting and drying may occur, and even the water may not be completely vaporized and removed, thereby affecting the moisture content of the freeze-dried product. And quality.
3. Determination of eutectic and co-melting points
The accurate measurement of eutectic point and inflection point of food materials is of great significance for optimizing the freeze-drying process of food, ensuring the quality of freeze-dried food and reducing energy consumption. At present, the measurement methods of eutectic point and co-melting point of food materials mainly include direct observation method of low temperature microscope, electric resistance method, differential scanning calorimetry (DSC), mathematical formula pushing algorithm, etc., and the most widely used one is resistance method. It has the characteristics of simple operation, good stability and wide measurement range.