Freeze drying uses a vacuum and freezing process to remove water from perishable foods and medicines, resulting in a product that can be stored for years without spoilage. This process is superior to heat dehydration as it preserves the flavor and texture of the food. Freeze-drying involves cooling the food or chemical, then placing it in a vacuum chamber where frozen water crystals change from solid ice to gas, leaving all solid food materials dehydrated. The resulting product can be stored in vacuum packages at room temperature.
Freeze drying, which scientists might call lyophilization, uses both a vacuum process and a freezing process to remove water from perishable foods and medicines. The result is a product that can be stored at room temperature for years without spoilage or packaged in limited storage spaces and reconstituted with water afterwards. Instant coffee makers often use a freeze-drying process, as do dietitians who create meals for campers, soldiers and astronauts. This process is also used in the pharmaceutical industry to preserve the integrity of air or moisture sensitive medicinal compounds.
Drying foods with heat for preservation is an ancient concept, but it has some drawbacks. The water inside the food is in liquid form, but the heat from the sun or other sources slowly converts it into a gas. As liquid leaves the food, the cell walls are often damaged and the essential flavor and texture of the food is lost. Adding water to heat-dehydrated foods doesn’t always restore flavor or texture. This is why freeze drying has an advantage over heat dehydration in the preservation process.
Freeze-drying first involves cooling the food or chemical, often far below the freezing point of water. At this point, all of the water contained within the food should have frozen into solid crystals. The basic structure of fruit, vegetables or meat has not changed, but the water content is solid. Half of the process has been done at this point through temperature reduction.
The drying process involves the use of a vacuum chamber. Frozen food or chemicals are placed in the vacuum chamber and the surrounding air is expelled. If this process were done at room temperature, the food would most likely be destroyed as the liquid water made its way to the vacuum chamber. However, frozen water crystals actually change from solid ice to gas, bypassing the liquid state altogether.
This process is called sublimation. It’s the same effect that makes solid dry ice practically disappear when struck with a hammer. During the freeze-drying process, solid water converts into a vapor-filled gas in the vacuum chamber, leaving all solid food materials dehydrated.
Once the water has been removed by freeze-drying, dried foods or chemicals are often stored in vacuum packages to prevent air and moisture from reaching them. These packets can be stored at room temperature, as bacteria and other harmful organisms cannot survive without air. Freeze drying also leaves small pores where the frozen water crystals were. That’s why instant coffee grounds mix so quickly and thoroughly with hot water. Freeze drying is also a popular process for creating “space-age” frozen desserts and backpack-friendly meals for hikers and campers.
Protect your devices with Threat Protection by NordVPN
