What is Freeze-Drying?
Freeze drying is the process of dehydrating frozen foods under a vacuum so the moisture content changes directly from a solid to a gaseous form without having to undergo the intermediate liquid state through sublimation. In this process, the product maintains its original size and shape with a minimum of cell rupture. Removing moisture prevents a product from deteriorating at room temperature.
The process is used for drying and preserving a number of food products, including meats, vegetables, fruits, and instant coffee products.
The dried product will be the same size and shape as the original frozen material and will be found to have excellent stability and convenient reconstitution when placed in water. Freeze dried products will maintain nutrients, color, flavor, and texture often indistinguishable from the original product.
Depending on the product and the packaging environment, freeze dried foods are shelf-stable at room temperature for up to twenty-five years or more, if canned, and between 6 months to 3 years if stored in a poly-bag container.
The main determinant of degradation is the amount and type of fat content and the degree to which oxygen is kept away from the product.
The Benefits of Freeze-Drying
There are several benefits to freeze-dried foods over dehydrating:
- Retains original characteristics of the product, including:
- Reconstitutes to original state when placed in water
- Shelf stable at room temperature – cold storage not required
- The weight of the freeze-dried products is reduced by 70 to 90 percent, with no change in volume
- The product is light weight and easy to handle
- Shipping costs are reduced because of the light weight and lack of refrigeration
- Low water activity virtually eliminates microbiological concerns
- Offers highest quality in a dry product compared to other drying methods
- Virtually any type of food or ingredient, whether solid or liquid, can be freeze-dried