一、工作原理及应用范围介绍Introduction of Working Principle and Scope of Application
真空冷冻干燥（也称“冻干"）是先将湿物料冻结到冰点以下，使水分变成固态的冰，然后在较高的真空度下使冰直接升华为水蒸汽，再用真空系统中的水汽凝结器将抽出的水蒸汽冷凝，从而达到将需干燥物料中的水分脱除获得干品的工艺过程。冻干技术现广泛运用于医药工业（如血 清、血浆、疫苗、酶、抗 生素）食品工业（如草莓、整虾、鸡丁、蘑菇片、蔬菜等）生物体的存活保存等。
The vacuum freeze drying (also called “freeze-drying") refers to the process firstly freezing the wet materials to below the freezing point and the water into solid ice, then directly sublimating the ice into water vapor at higher vacuum degree, condensing the pumped water vapor by the vaporcondenser in the vacuum system, and finally obtaining the dry materials with water removed. Now, the freeze-drying technology is widely applied in the survival storage of living bodies in the medical industry (such as serum, plasma, vaccine, enzyme and antibiotic) and food industry (such as strawberry, shrimp, diced chicken, sliced mushroom and vegetable).
1.The drying is carried out below triple point pressure of water, and the materials are under high anaerobic condition; in addition, the drying is carried out at low temperature, so there is no overheat of materials. Therefore, this mode is especially applicable to drying of material very sensitive to heat and easy to oxidize. For example, for the food dried by using this technology, its color, taste, smell, vitamin C and other nutrient substances of fresh food will be reserved.
2.As the materials are frozen before sublimating and dehydration with stable solid frame formed, the solid frame will keep unchanged basically after the water is vaporized, so the solid structure and original appearance of dry materials will not be changed. The finished products with porous structure have ideal instant solubility and fast reconstitution property.
3.As the water in the materials exists in the ice crystal form after pre-freezing, the inorganic salt substances dissolvedin water will be distributed in the material uniformly. During the sublimation, thesubstances dissolved in water will be precipitated, avoiding the surface hardening due to surface precipitation of inorganic salt carrying by water of material while moving to the surface.
4.The materials are in frozen state with very low temperature, the heat source temperature for heat supply may be normal temperature, or the heater with low temperature can meet the requirement. If the freezing chamber and drying chamber are separated, it is not required to insulate the drying chamber, and little heat loss may be caused, so it is very economical to recycle the heat energy.
三、工艺流程图Process flow diagram
Technical parameters (the values in the table below are for reference in type selection only)