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Mar 23, 2021
Chemical Compound Responsible For Cannabis Odor Identified

A research team comprised of Byers Scientific, Iowa State University and Texas-based odor experts report isolation and identification of the volatile chemical which appears to be primarily responsible for the downwind skunky-like environmental odor complaints which have been commonly reported for commercial cannabis and industrial hemp growing operations.

By employing a triangulation approach of analytical chemistry (i.e., SPME fiber, Gas Chromatography-Mass Spectrometry and GC-Olfactometry analysis), leaf enclosure study and field observation, the team of researchers were able to isolate, identify, measure and ultimately conclude that the compound 3-methyl-2-butene-1-thiol (i.e., 321 MBT), is the primary source of the traditionally objectionable odor of cannabis.

The compound is also the same odorous volatile chemical that has previously been reported to carry responsibility for the skunky-like aroma and flavor defect in light-struck beer.

Historically, the objectionable odor of cannabis has often been tied to terpenes (i.e., unspecified members from among the vast array of naturally occurring volatile hydrocarbons which are more commonly associated with the familiar aromas of citrus and other fruits, eucalyptus leaves and hydrocarbon solvents, etc.). This reported discovery of the actual link between ‘skunky’ cannabis and 321 MBT supports the more persuasive expectation of a sulfur component within the chemical profile of the cannabis plant emission. In retrospect, the relationship between ‘skunky’ beer and cannabis should probably not be surprising since the ‘skunky’ beer odor comes from hops which are in the same plant family (Cannabaceae) as cannabis and hemp. Perhaps more surprising; however, previous odorant prioritization efforts by the collaborative consultants have also shown MBT to represent an odor impact priority for actual skunk oil, as extracted from skunk musk gland. In these prior investigations, MBT was adjudged as second in odor impact priority, second only to E-2-butene-1-thiol.

While this discovery is exciting and represents true progress in the scientific understanding of the source of the distinctive and divisive odor of cannabis, the researchers caution that this is only the first critical step in fully researching this issue. Leaf enclosure studies reveal other thiols present in the plant emissions and, more importantly, other compounds in the plant’s gas-phase emissions and atmospheric reactions may significantly affect the perception and measurement of 321 MBT. Efforts are currently underway to further evaluate the odor and the most appropriate manner of mitigation.




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