Dear Fabiano,

This would depend on how the sample was prepared for freeze drying, the atmosphere over the sample, and how the sample was stored after drying.  Also - what kind of activity are you wanting to preserve?

It seems that the most widely used solution is freeze drying, as when done with care can be used to preserve chemical and protein activity for some years. [Most of the worlds vaccines and antibody based drugs are freeze dried - with shelf life of 6 to 36 months].    It would probably be best to fill the space over you sample with inert gas (as vaccine manufacturers do) and also to store in the freezer.  When you want to use a sample again, warm it up slowly and reconstitute with care.

Kind regards,

Rob

Hi friend! Thsnks for the answer!

I made lyophilized plant extract by heating for saponins extraction. Since then the powder has not changed its visual characteristics. It remains the same odor and visual appearance, without water absorption and the granules remains the same. Are the chemical and effective characteristics still conserved as well? I stored these extracts in a 50 ml falcon protected from the direct incidence of light.

Thanks again!