A method and apparatus for evaporative cooling of materials within a vacuum chamber by maintaining a controlled partial pressure environment. The method involves sealing material inside a chamber, reducing the internal pressure using a vacuum pump, and simultaneously introducing external gassuch as ambient air, nitrogen, or inert gasesinto the chamber. A constant partial pressure is maintained by balancing the gas input and vacuum pump operation, allowing for efficient evacuation of vaporized liquid without recondensation. The system can operate with either constant or variable flow rates for both gas input and vacuum pumping, depending on desired cooling conditions, chamber size, and material characteristics. The apparatus includes a sealable vacuum chamber, at least one external gas inlet, and a vacuum pump configured to sustain the target partial pressure.

Methods and apparatus for sterilizing plant material include disposing plant material in a sub-atmospheric pressure environment, dispersing a non-toxic, non-polymerizable gas into the sub-atmospheric pressure environment, applying an electric field to change the gas into cold plasma, and maintaining exposure of the plant material to the cold plasma until substantially sterilized plant material is obtained, wherein an amount of at least one active constituent in the plant material is substantially unchanged by the sterilizing. The plant material may be cannabis.