Vacuum drying is the process of transition of a substance from a solid to a gaseous state without a liquid phase.
Advantages of the vacuum drying process
The advantage of vacuum drying is that this method ensures nutrients, trace elements and vitamins are preserved for a period from two to five years. This drying method has successfully proved itself both in chemical and food industries. Vacuum drying method is also successfully used in pharmaceutical production.
There is no need to use preservatives, flavors and dyes with vacuum drying. Therefore material costs for the purchase of raw materials are reduced, and the time of the drying process is also significantly shortened.
Vacuum drying makes it possible to reduce the particles of food or chemical powder in volume without the destruction of their structure and the use of additional «masking» substances.
Another undoubted advantage of vacuum drying is the preservation of organic compounds with a complex structure. This is especially important in the production of food powders. As a result of oxidation and high temperatures, the amount of nutrients in the product inevitably decreases. Therefore, toxic or expensive solvents are often used with other drying methods, especially with the aim to shorten the drying time. There is no need to control the moisture content of the substance and its interaction with the environment, since it affects the moisture content.
Scope of application of vacuum drying
Vacuum drying has a wide range of applications. It continues to be successfully applied to the development of nutrition in the space, military and defense industries, and has found wide application in canning, in the production of children’s, dietary and medical products. Vacuum drying has successfully proven itself in the production of coffee, tea, dairy raw materials, seafood and vegetable mixtures. Food dyes and pigments are produced using vacuum drying. Sugar-containing foods are particularly temperature sensitive. Therefore, a vacuum drying method for processing such products will be the most acceptable.
Vacuum drying process
The main influencing force is not the temperature regime, but the pressure. Vacuum freeze drying is used in the food industry most often. It is also called sublimation or lyophilization.
Fresh frozen foods and food powders are placed in a vacuum type chamber, and then the following principle is applied: low temperature below zero degrees leads to two states — liquid and gaseous. Depending on what kind of end product you want to get, you need to adjust the temperature carefully. First, the product is frozen, then dried and, if necessary, dried to the final condition.
The vacuum level should be different for the production of a particular powder. Its optimal value is from 10-2 to 100 mm. Hg.
The quality of vacuum drying depends on the intensity of freezing directly. The less ice crystals are formed on the surface of the powder, the more intensive the process of their evaporation occurs and the better product will be on the output.