Fruit freeze dryer

　There are various methods to freezing the product. Freezing can be done in a freezer, a chilled bath (shell freezer) or on a shelf in the freeze dryer. Cooling the material below its triple point ensures that sublimation, rather than melting, will occur. This preserves its physical form.

　　Freeze drying is easiest to accomplish using large ice crystals, which can be produced by slow freezing or annealing. However, with biological materials, when crystals are too large they may break the cell walls, and that leads to less-than-ideal freeze drying results. To prevent this, the freezing is done rapidly. For materials that tend to precipitate, annealing can be used. This process involves fast freezing, then raising the product temperature to allow the crystals to grow.

　　Primary Drying (Sublimation) Phase

　　Freeze drying’s second phase is primary drying (sublimation), in which the pressure is lowered and heat is added to the material in order for the water to sublimate. The vacuum speeds sublimation. The cold condenser provides a surface for the water vapor to adhere and solidify. The condenser also protects the vacuum pump from the water vapor. About 95% of the water in the material is removed in this phase. Primary drying can be a slow process. Too much heat can alter the structure of the material.

　　Secondary Drying (Adsorption) Phase

　　Freeze drying’s final phase is secondary drying (adsorption), during which the ionically-bound water molecules are removed. By raising the temperature higher than in the primary drying phase, the bonds are broken between the material and the water molecules. Freeze dried materials retain a porous structure. After the freeze drying process is complete, the vacuum can be broken with an inert gas before the material is sealed. Most materials can be dried to 1-5% residual moisture.

　　SUBLIMATION

　　Sublimation is when a solid (ice) changes directly to a vapor without first going through a liquid (water) phase. Thoroughly understanding the concept of sublimation is a key building block to gaining knowledge of freeze drying.

　　As shown below on the phase diagram for water, low pressures are required for sublimation to take place.

　　Sublimation is a phase change and heat energy must be added to the frozen product for it to occur.

　　Sublimation in the freeze drying process can be described simply as:

　　FREEZE - The product is completely frozen, usually in a vial, flask or tray.

　　VACUUM - The product is then placed under a deep vacuum, well below the triple point of water.

　　DRY - Heat energy is then added to the product causing the ice to sublime.

　　If you have a lyophilizer, freeze dryer, etc., you need to know the quotation, please go to # to find the phone + 86-10-58895379 or send an email: info@bjsyhx .com.cn contact us, we will contact you in the first time.

　There are various methods to freezing the product. Freezing can be done in a freezer, a chilled bath (shell freezer) or on a shelf in the freeze dryer. Cooling the material below its triple point ensures that sublimation, rather than melting, will occur. This preserves its physical form.

　　Freeze drying is easiest to accomplish using large ice crystals, which can be produced by slow freezing or annealing. However, with biological materials, when crystals are too large they may break the cell walls, and that leads to less-than-ideal freeze drying results. To prevent this, the freezing is done rapidly. For materials that tend to precipitate, annealing can be used. This process involves fast freezing, then raising the product temperature to allow the crystals to grow.

　　Primary Drying (Sublimation) Phase

　　Freeze drying’s second phase is primary drying (sublimation), in which the pressure is lowered and heat is added to the material in order for the water to sublimate. The vacuum speeds sublimation. The cold condenser provides a surface for the water vapor to adhere and solidify. The condenser also protects the vacuum pump from the water vapor. About 95% of the water in the material is removed in this phase. Primary drying can be a slow process. Too much heat can alter the structure of the material.

　　Secondary Drying (Adsorption) Phase

　　Freeze drying’s final phase is secondary drying (adsorption), during which the ionically-bound water molecules are removed. By raising the temperature higher than in the primary drying phase, the bonds are broken between the material and the water molecules. Freeze dried materials retain a porous structure. After the freeze drying process is complete, the vacuum can be broken with an inert gas before the material is sealed. Most materials can be dried to 1-5% residual moisture.

　　SUBLIMATION

　　Sublimation is when a solid (ice) changes directly to a vapor without first going through a liquid (water) phase. Thoroughly understanding the concept of sublimation is a key building block to gaining knowledge of freeze drying.

　　As shown below on the phase diagram for water, low pressures are required for sublimation to take place.

　　Sublimation is a phase change and heat energy must be added to the frozen product for it to occur.

　　Sublimation in the freeze drying process can be described simply as:

　　FREEZE - The product is completely frozen, usually in a vial, flask or tray.

　　VACUUM - The product is then placed under a deep vacuum, well below the triple point of water.

　　DRY - Heat energy is then added to the product causing the ice to sublime.

　　If you have a lyophilizer, freeze dryer, etc., you need to know the quotation, please go to # to find the phone + 86-10-58895379 or send an email: info@bjsyhx .com.cn contact us, we will contact you in the first time.