Can I Freeze Dry Foods At Home?

by John Ranicar October 10, 2016

Can I Freeze Dry Foods At Home?

Well the answer is yes and no!

Freeze drying products like our commercially manufactured Forager Fruits and Forager Providore lines requires very specific and high tech equipment. We use stainless steel vessels that are reinforced to withstand enormous vacuum pressures that are applied to create the environment in which foods will freeze dry and a range of other machinery to provide heating, cooling and vacuum - all of which is computer controlled.

A quick recap on the process. First we prepare our foods that are to be freeze dried by washing, then slicing if required. The food must be frozen to at least -20 degrees C before it is placed in the freeze drier chamber. Once the trays of food are frozen and placed in the freeze drier chamber, a vacuum pump is used to effectively remove all of the air thus reducing the air pressure within the chamber. The pressure can get as low as 10 pa which is close to the pressure in outer space!

It is this low air pressure that caused the drying process. At less than 100 pa, water will boil when frozen at -20 degrees C. It literally turns from ice to vapour (steam) without becoming liquid as it would at normal atmospheric pressure. Our machine allows us to add a gentle amount of heat to the trays of frozen product which helps to speed up the process. Despite the ice becoming steam, the product remains frozen which preserves the size, shape and nutritional values.

The next step is to capture that vapour which is done by having pipes in the freeze drier chamber that are kept at -50 degrees C. The vapour re-freezes onto these pipes and over the 24 hours that it takes to dry a whole batch, all of the moisture migrates from the product to these pipes. At the end of the cycle, we thaw this water and start again.

So, to freeze dry at home you would require some very specialised equipment, some experience to manage the process and a fat wallet to pay for it all! Hence, At Forager Foods we freeze dry for you and are even happy to take orders for specialised products.

I did start by saying yes and no. The yes answer would mean copying what the Inca people did some 10,000 years ago. They would harvest their food, carry it up into the mountains above the winter snow line and leave it in caves. By the following summer, the low air pressure in the mountains combined with the freezing conditions would literally freeze dry their foods, preserving it for future use. Hopefully you have a mountain nearby!

 




John Ranicar
John Ranicar

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