Freeze drying remove the moisture out of the food, which allow the food to last longer. If the food still contain moisture in the center of the food products, that food will absorb moisture while in storage, which will make the food either soften or have an incorrect flavor. In order to prevent the food from becoming soft or having an incorrect flavor, the freeze drying process must be managed correct.
One way of managing the freeze drying process is by utilize a time chart for freeze drying, which can tell how long different types of food should be freeze dried. To begin the freeze drying process, the food must first be froze solid. Once the food is solid, an vacuum is applied to the machine, as well as the machine applies heat to the food to turn the ice in the food to vapor.
How to Freeze Dry Food Correctly
The length of time that the food is freeze dried will depend upon the type of food. For instance, fruits contain different sugars then meats or vegetables, so the drying times for fruits will be different than meats and vegetables. Additionally, it is best to not place different types of foods on the same freeze drying tray, as the foods that dry quick will be done with the freeze drying process before the foods that take longer to dry.
In order to prepare the food, the food must be slice into thin pieces, such as quarter inch slices. Foods that are thick will take longer to dry than thin sliced pieces of the same food. Additionally, it is best to not place too many food on the drying tray, as this may lead to the tray becoming clogged, which will make the freeze drying process take longer to complete.
Foods such as vegetables should be blanched prior to freeze drying, as blanching will kill the enzyme that retain the moisture within the vegetables. It is also important to make sure that the food to be freeze dried is cold when it is load into the freeze dryer. If warm food is load into the freeze dryer, the cycle will take longer to complete.
A freeze drying cycle includes several step, such as vacuum creation, primary drying, and final drying. During the final drying step, chunky foods may be freeze dried longer, as they tend to retain moisture in there centers. Additionally, it is possible to determine if the food is dry by weighing the tray of food during the freeze drying process; the weight will remain the same if the food is dry.
It is not a good idea to visually inspect the food to determine if it is dry. Instead, it is best to take the thickest piece of food and check for a few different indicator of whether or not the food is dry. First, the food should snap sharp when broken.
Additionally, the food should not feel cold in the center of the food, as well as not create fog and steam when reheated. If the food does not create steam when reheated, the moisture has been successfully remove from the food. Due to the type of food, different amount of time may be required for each type of food.
For example, the majority of fruits require between 20 and 30 hours of freeze drying, while denser meats may require more than 40 hours of freeze drying. Additionally, foods like soups or yogurt drop may require between 18 and 26 hours of freeze drying. Each of these times may change based off the thickness of the product that is to be freeze dried, as well as the amount of sugar that is contain in those products.
Consequently, it is important to log each of these result. The results should include the starting weight of the product, the thickness of the food, the length that the product was freeze dried, and the test for dryness of the product after the freeze drying cycle. The last step in the freeze drying process is the storage of the freeze dried food.
The food must be store correctly so that the food does not absorb moisture from the storage area. The food should be allowed to completely cool after being freeze dried, and then placed into bags. The bags should be Mylar bags with oxygen absorber.
Additionally, the food should be store on dark shelves in the storage area, as the food may fade in color if stored on light shelves. Finally, the gaskets of the freeze dryer should be cleaned and the operator should defrost the machine between every cycle of freeze drying food.