Difference Between Freeze Dried and Air Dried Food
What is the difference between air drying (dehydration or dried) and freeze drying?
Air drying / Dehydration / Drying
In layman term, dried food removes water and converts it to water vapour (from liquid to gas).
It is a process that dries the food with air or a heating element. The moisture evaporates out of the food via this drying process.
In layman term, freeze dried food removes ice and converts it directly to water vapour (from solid to gas).
Freeze-dried food retains the most nutrition, shape and flavor as compared to other drying methods.
It removes moisture from the food through a vacuum system which acts on the frozen material, removing ice from the food and converting it directly to water vapor. Since the water is removed from the food in a frozen state, cell structure remains intact.
FREEZE DRYING VS AIR DRYING
Both freeze-dried and air-dried products can retain the appearance and color of the original fresh product but freeze-drying keeps cell structure intact more effectively than the air-drying process and hence looks less wrinkled.
Freeze Dried fruits
Both freeze-dried and air-dried products are made up 100% of the raw product. Nothing is added during the process itself and only water is removed even though there are a lot of dehydrated fruits that has added sugar.
3. WATER CONTENT
Water content is lower for freeze-dried products, although it varies from product to product in both categories. An average for freeze-dried is around 1% water content, and an average for air-dried is around 8%.
Since the cell structure remains intact for freeze-drying process, they rehydrate very quickly when they are in contact with water again. Our instant quinoa takes only 1 to 3 minutes to rehudrate to soup whereas most air-dried products take closer to twenty to thirty minutes.
So even though many of the quinoa in the market are marketed as instant, they are dehydrated. So it will take a long time to rehydrate. Pouring water over freeze dried fruits will return it to the original shape and texture.
5. SHELF LIFE
Since air dired food has higher water content, it will have higher potential for bacterial growth leading to shorter shelf life. Actual length of shelf life for any given freeze-dried product depends on packaging, storage temperature and the product itself. The longest that freeze dried food can last with proper packaging is 25 years.
6. FLAVOR / TEXTURE
Air-dried food are generally more "sticky" and taste denser whereas freeze-dried food are generally crunchier and taste closer to the original food.
Freeze-dried food is akin to fresh food without water retains most of its nutrition whereas air-drying may breaks down certain nutritional elements.