While freeze drying, when the product chamber was turned on, I opened the freeze dryer for a moment to adjust the sample. After that, it was not opened for a single moment. But, after completing the freeze drying, the sample was jelly-type substance (GelMA) and the moisture was there. What can be the suitable reasons for that? Can it be the opening of the freeze dryer when product chamber was turned on or it is something else.
Depending when you opened the system, yes, most likely you suffered cake collapse and did not get good refreezing.
In any vacuum dryer, including a freeze dryer, the pressure in the system controls the boling point = sublimation point of the solvent(s) in the sample. Solvents here includes water. If the BP / Sub Point is less than the freezing point, the sample will freeze due to pressure. Retrun the pressure of atmosphere, say by opening the system ....
Helpful overview on the process can be found here:
https://scientificproducts.com/category/freeze-drying/
Rob Darrington, can another reason be the maximum moisture removal capacity of freeze dryer from a substance?
It could. Freeze drying is a balance, if one part of the system is not in balance then bad things can happen!
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