freeze drying

[crazydave]

is it possible to freeze dry your own rice in a normal freezer?

you dont seem to be able to get it in this country, all mine is from aussie rat packs and I'm down to my last packet

 

[bikething]

I don't think it's as easy as that :

Freeze drying (also known as lyophilization or cryodessication) is a dehydration process typically used to preserve a perishable material or make the material more convenient for transport. Freeze drying works by freezing the material and then reducing the surrounding pressure and adding enough heat to allow the frozen water in the material to sublime directly from the solid phase to gas

more info here

 

[rik_uk3]

The five minute rice you buy is freeze dried stuff. You can boil rice and dehydrate it. The 5 min stuff is BOGOF 69p at Iceland stores

 

[bikething]

The five minute rice you buy is freeze dried stuff. You can boil rice and dehydrate it. The 5 min stuff is BOGOF 69p at Iceland stores

My nearest Iceland is 25 miles away - It'll cost me a fiver in petrol

Is there any weight advantage of freeze dried rice over normal rice? or is it just the cooking time that's different?

 

[crazydave]

is that plain rice or flavoured?

the key difference is that with freeze dried rice I can add cold water and it will fluff up in a few minutes.

I was looking in asda today and there was 5 min packet rice next to 20 min stuff.

 

[clcuckow]

You need a partial vacuum to freeze dry and I dought that a domestic freezer will get down to -50C

 

[crazydave]

freezers create a partial vacuum dont they? at least due to the difference the cold creates in the air pressure, isn't that why you get freezer burn as it dehydrates? thats what got me thinking

 

[mortalmerlin]

In freeze drying you reduce the pressure and temperture then when you raise the temperature the water will sublime rather than go into a liquid phase. Bring the pressure back up and your food is dry.

As far as I understand the principal, at normal pressure water can be solid liquid or gas but at much lower pressure is can only be a solid or gas, it becomes a sublimating substance.

But before you get any ideas involving a vacuum cleaner, if you pump all the air out of your freezer I suspect it will just implode