Can Steam Treatment be used to Decontaminate Cannabis?

Steam treatment is one of the most widely used methods for microbial decontamination of herbal drugs. According to the USP, this is largely because other methods, such as fumigation and ionizing radiation, have become restricted or prohibited for use on herbal raw materials in many countries. Furthermore, an increasing percentage of herbal materials are produced according to organic production regulations, which limits the decontamination processes to a few methods.

Use of Steam Treatment for Microbial Decontamination of Herbal Drugs

Thermal processes (e.g., dry heat, infrared heating, steam) are widely used to decontaminate botanicals, but depending on the type of herbal material and the treatment method, organoleptic (e.g., color, odor, taste) and physicochemical (e.g., water activity, moisture content) properties can be adversely affected, as well as content and composition of volatile compounds.

There are two basic steam treatment methods: Batch (in a chamber) and continuous steam processing (on a conveyer). Steam treatment may be an acceptable method for botanicals that are not dependent on essential oil content and composition for quality and efficacy. In 2021, Jerushalmi et al. subjected medical cannabis (Cannabis sativa L.) to short pulses of steam (10-, 15-, and 20 s exposure) for reduction of fungal contamination. A starting TYMC (total yeasts and molds) value of 10^(4.4 ± 1.02) in the untreated control was reduced to 0, 2, and 0 colony-forming units (CFU)/g for the 10-, 15-, and 20 s steam exposure treatments. A second sample with a TYMC value of 10^(3.05 ± 1.15) CFU/g reduced to 0 in all three exposures (Jerushalmi et al., Effects of steam sterilization on reduction of fungal colony forming units, cannabinoids and terpene levels in medical cannabis inflorescences. Sci Rep. 2021;11(1):13973).

For more information please see the draft USP chapter <1120> Ensuring Microbiological Quality of Articles of Botanical Origin published in Pharmacopeial Forum.