A system for applying a gaseous biocide to a foodstuff, comprising: a treatment chamber having a vapor partitioning passage in which biocide is applied to the foodstuff; a conveyor extending from a first location outside the treatment chamber for conveying the foodstuff, through a first aperture in a wall of the treatment chamber, through the vapor partitioning passage, through a second aperture in a wall of the treatment chamber, and terminating at a second location outside the treatment chamber; an air distribution system supplying air into the treatment chamber, and an air extraction system through which air and remaining biocide is drawn from the treatment chamber. Pressure within the treatment chamber is maintained lower than outside the treatment chamber and lower than within the vapor partitioning passage, whereby air drawn into the treatment chamber is directed away from the vapor partitioning passage and gaseous biocide is prevented from exiting.

A moisture-activated sulfur dioxide (SO.sub.2) release system is disclosed for postharvest preservation of fruits, vegetables, and other fresh plant products. The system comprises a composition including sodium metabisulfite (SMBS) and citric acid that, upon exposure to humidity, rapidly generates SO.sub.2 gas to suppress fungal growth. Various deployment systems enable immediate or sustained release based on packaging conditions and crop type. The system provides a safer alternative to traditional SO.sub.2 fumigation, and provides improved decay control and extended shelf life.

Methods and systems are provided for infusing a crystalline and/or porous solid with a desired fluid, particularly an antimicrobial agent, as well as infused crystalline and/or porous solids produced thereby. Solids which may be infused with an antimicrobial agent according to the invention include erythritol, table salt, table sugar, baking soda, calcium carbonate, acetic acid, ascorbic acid, and marshmallow.