A study published recently in the American Chemical Society’s (ACS) journal Omega suggests that terpenes are only part of the picture when determining what compounds are responsible for the aroma of cannabis.
The study argues that different samples of cannabis that contain similar terpenes can smell wildly varied depending on the presence or absence of other nonterpenoid volatile compounds. The researchers also note that “cannabis labelling or certificates of analysis (COAs) that contain only terpene information thus may mislead consumers or producers into believing that these compounds are the sole source of a given product aroma.”
The researchers cite another recent study “that found that cannabis grown across the United States falls into three major classes [based on terpene constituents]: terpinolene/ß-myrcene, D-(+)-limonene/ß-caryophyllene, or ß-myrcene/pinene dominant varieties.” They proceed to note that, problematically, “this study showed varieties with very different aroma characteristics are often found in the same cluster, which is contrary to the paradigm that these dominant terpenes dictate their aromatic character.”
They go on to provide some examples of this. “For instance, Dogwalker OG, which possesses a skunky and woody aroma, was found in the same D-(+)-limonene/ß-caryophyllene cluster as Tropicana Cookies, which possesses an intense citrus and tropical aroma. Purple Punch, which possesses a sweet, grape-like scent, was also found in this cluster. This discrepancy suggests that while these classifications may be helpful for chemotaxonomic purposes, they lack the chemical information necessary to differentiate these varieties from an aroma perspective,” concluding simply that “the importance of terpenes appears to be overstated.”
For the purposes of this study, the research team analyzed “the volatile chemical profiles of 31 cannabis ice hash rosin extracts with a wide aromatic diversity using 2-dimensional gas chromatography coupled with time-of-flight mass spectrometry and flame ionization detection.” The results indicated “a myriad of nonterpenoid compounds that strongly influence the unique aromatic properties of cannabis.”
Interestingly, their findings show that while the majority of these nonterpenoid compounds occur in much smaller quantities than dominant terpenes, they punch way above their weight in terms of their effect on the plant’s aroma.
In particular, they identified “a new class of tropical volatile sulfur compounds (VSCs) that are major contributors to certain varieties with a strong citrus or tropical fruit aroma, while skatole (3-methylindole), a highly pungent compound, was identified as a key aroma compound in savory/chemical varieties.”
Ice hash rosin was used in this study because it has less plant tissue by weight than cannabis flower and further concentrates the molecules in question.
The rosin was then given to a sensory panel for analysis, with participants asked to group the samples into three categories: exotic fruity, prototypical, or exotic savory. These data provided researchers “with the framework to relate the chemical composition of each variety to their aromatic properties.” These results were then compared with chemical analysis to determine which compounds correlated with which perceived aromas.
Researchers “discovered that there exists [a] unique class of VSCs that produce tropical nuances–sulfur containing compounds that produce more citrus, fruity, sulfuric aromas–that includes 3-mercaptohexanol (3MH), 3-mercaptohexyl acetate (3MHA), and 3-mercaptohexyl butyrate (3MHB). These compounds have extremely potent aromas, comparable in strength to prenylthiol and prenylthioacetate. All three are found in a multitude of tropical fruits such as passionfruit and grapefruit. 3MH and 3MHA are also found in certain grapes and hops, which can translate to their presence in both wine and beer.”
In conclusion, the authors write that their results “yield a more complete understanding of the unique aromas that cannabis produces and help establish these nonterpenoid compounds as an important part of the phytochemistry of cannabis.”
And what’s more, “the discovery that terpenes have less influence on the differentiating characteristics of the aroma of cannabis than traditionally thought may have important ramifications for the legal cannabis industry related to product labelling and marketing, laboratory testing, and quality indicators for end consumers and producers alike.”
* The study cited above was conducted by a group of researchers associated with Abstrax Tech, an American company that specializes in the manufacture and sale of aromatic compounds from cannabis and other plants.