| Author | Message | ||
     Matthew |
I know you need a vacuum to freez dry something (vacuum pump project) but how do you freez dry something. Do you need to put it in a vacuum and freez it or is it just puting something in a vacuum and letting it dry? | ||
| Simon Quellen Field (Sfield) |
You freeze something, then lower the air pressure to allow the ice to sublime. This retains the shape of the object, but replaces the water with air when the air is let back into the chamber. | ||
| Matthew |
Cool, thanks. | ||
| Anonymous |
Does the frozen object need to be at a specific temperature? Colder than freezer temperature? And would the vacuum pump project work just fine? | ||
| Anonymous |
Freeze your sample by dipping your container in a alchol-dry ice bath that will be far colder that you can freeze in your freezer. When completely frozen, place sample in vac chamber and pump down (probably 1-3 days with a heavy-duty rotary vane vac pump. I'll have to look up the degree of vacuum vs. time to dry --- I'll get back to you. Works great to lyophilize certain species of edible fungus. | ||
| balavant patil Unregistered guest |
how to freez dry aloevera juice? what temperature is required?Is it possible to do it without vacuum? | ||
| Simon Quellen Field (sfield) Senior Member Username: sfield Post Number: 307 Registered: 12-2004 |
You need a vacuum. You also will generally want two chambers, one for the stuff being dried, and a second chamber kept at a much colder temperature, so the water vapor will condense there and thus be removed. A Google search will tell you much more, and give you diagrams. | ||
| Evan Lynn Mills (Wwindmills) New member Username: Wwindmills Post Number: 1 Registered: 1-2006 |
My brother and I were freeze drying small, 20 to 40 gram items with a freezer and a fan blowing across the samples. They dried in three days and the body water content was over 90%. We were selling the freeze dried items commercially. | ||
| J N (Newty) New member Username: Newty Post Number: 2 Registered: 5-2009 |
Water sublimes more slowly at normal air pressure, but it does eventually move. I accidentally freeze-dried something in a regular household freezer. I left an open container of wet carrot pulp in an open container and forgot about it for a few months. When I went to clean out the freezer, I found the pulp dried into a bone-dry fluff that resembled bright orange dryer lint. It rehydrated quite nicely, too, but I was reluctant to find out how it tasted. |
