freezedrying - question of the workingprinciple (Jun/20/2008 )

I have found this on another forum and I found it an intersting question:

"to have a good sublimation of the freezed product, the product itself needs to be on a higher energy level then the environment around it"

I think they mean that you need to put energy in your product and thus the product itself needs to be on a higer energy level.
Or is there another reason why they state this?

besides that: can you have sublimation of a product of the energy around the product is higher?
I think yes, because the environment around the product can then put his energy in the product and thus cause sublimation, but is this correct? It seems a bit strange and a circle movement (=> energy from outside in the product to sublimate it, and by sublimating it you will get vapor with a lot more enery outside the product and thus making the energylevel outside higher again (note that this is in a closed environment, otherwise the engery could go away...?)


any ideas?


and then another question: what pressure do you guys use when freezedrying? How many mbar or torr or pascale do you guys use during the primary drying?

maybe the negative pressure is considered an energy investment