Freeze drying method
Freeze drying method is the sublimation of water content from frozen food. The freeze drying method occurs under a vacuum and causes the fruit, or vegetable, or coffee, solidly frozen during the process. Shrinkage is eliminated or minimized, and a near-perfect preservation results. Appling freeze drying method, the freeze dried food lasts longer than other preserved food and is very light, which makes it perfect for space travel. The cold mountain temperatures froze the food and the water inside slowly vaporized under the low air pressure of the high altitudes. The purpose of freeze drying method is to remove a solvent from dissolved or dispersed solids. Freeze drying method is used for preserving materials that are unstable in solution. In addition, freeze drying method can be used to separate and recover volatile substances as well as to purify materials. During freeze drying, moisture sublimes directly from the solid state to vapor, thus producing a product with controllable moisture that has no need for cooking or refrigeration and retains its natural flavor and color.
Freeze drying method is used interchangeably depending on the industry and location where the drying is taking place. Controlled freeze drying keeps the product temperature low enough during the process to avoid changes in the dried product appearance and characteristics. It is an excellent method for preserving a wide variety of heat-sensitive materials such as proteins, microbes, pharmaceuticals. Freeze drying method in the freeze drying process can be described simply as 3 steps. Firstly the product is completely frozen, usually in trays or vials. Then the product is placed under a deep vacuum, well below the triple point of water. Heat energy is then added to the product causing the ice to sublime. This continues for many hours while the material gradually dries out. The process takes so long because overheating the material can significantly change the composition and structure. Additionally, accelerating the sublimation process could produce more water vapor in a period of time then the pumping system can remove from the chamber. This could rehydrate the material somewhat, degrading its quality.
In addition to providing an extended shelf-life, successful freeze drying method should yield a product that has a short reconstitution time with acceptable potency levels. The process should be repeatable with well defined temperature, pressure and time parameters for each step. Visual and functional characteristics of the dried product are also important for many applications.