Freeze Drying? Wassup with that?
Freeze drying has been around since the early 1900’s, originally implemented to preserve blood serum during World War II, and later used to preserve heat-sensitive substrates. In recent years there’s been an exponential surge in the availability of freeze dried products and foods.
But exactly what is freeze drying? And why is it so important to our food industry?
Freeze drying food is the process by which the food’s water is crystallized at very low temperatures and then removed by a process called sublimation: converting the crystalized water to gas without melting in the process.
There are 3 stages involved in this process:
- 1.Freezing stage: Lowering the food’s temperatures to below freezing (-30 degrees Fahrenheit) Considered one of the most critical parts of the freeze drying process
- 2.Drying phase: applying a high vacuum plus low heat in order to vaporize the water from the food. This part of the process removes up to 95% of the food’s water content, and relies heavily upon the use of a specialized vacuum pump, drying trays and condenser. The condenser attracts the vapors being sublimed off the food and condenses them back into ice on the surrounding chamber’s drum.
- 3.Final drying phase: removes the remaining 1%-4% of water from the remaining food.
The end result: a water-free, extremely shelf stable food product which, under proper storing conditions, can keep food fresh for up to 25 years.
How is this even possible? By removing its water content, any bacteria that might be present is rendered incapable of replicating and spoiling the food.
The incredible shelf stability of freeze dried foods makes these products appealing to retailers, backpackers, campers, as military rations, and as a source of survival food storage. There’s a growing movement towards freeze drying for home use. More on this topic to be discussed at a later date.