Role of terpenes in cannabis smell ‘overemphasised’ study suggests

The results of a recently published study show that minor compounds known as VSCs, and not terpenes are the main reason that cannabis projects such a strong smell. 

New data published in the American Chemical Society’s journal Omega shows that minor non-terpenoid compounds, although accounting for a minute percentage of the samples’ mass, contributed to most of the aroma, and terpenes contributed less. 

“While these compounds contribute to the characteristic aroma of Cannabis sativa L. and may help differentiate varieties on a broad level, their importance in producing specific aromas is not well understood. Here, we show that across Cannabis sativa L. varieties with divergent aromas, terpene expression remains remarkably similar, indicating their benign contribution to these unique, specific scents” the study says.

The findings hold importance as consumers often choose a specific strain because they associate the aroma of it with that of another strain that produced a specific effect, and since terpenes are often cited as the main influence behind the pungent aroma of cannabis the strain’s terpene profile becomes a factor that influences that choice.

The study authors provide an example in their comparison of three strains that had been classified together because they share the same terpene profile: Dogwalker OG, Purple Punch, and Tropicana Cookies. Although all three contain the terpenes limonene and caryophyllene, they all have distinctly different aromas: Dogwalker OG is known to have a skunky and woody aroma, Tropicana Cookies holds citrus and tropical notes, and Purple Punch is famed for its sweet grape-like tang. 

To explore their hypothesis the team, from Abstrax Tech, a U.S. company that specialises in aromatic compounds of cannabis and other plants, used sensory and chemical analyses to compare the aroma of ice hash rosin products extracted from 31 different strains.

Noting that many strains gave off similar aromatic scents the researchers devised three primary classes characterised by aroma: sweet exotic, prototypical, and savoury exotic. By separating the 31 ice hash rosin samples into these classes researchers were able to identify many strains with similar terpene profiles that were placed in different aromatic classes.

The authors explain the processes used, and their findings, “Detailed chemical analysis using two-dimensional gas chromatography revealed that minor, non-terpenoid compounds are responsible for this discrepancy. While found in low concentration, often accounting for less than 0.05% of the mass of the samples, their odour impact can be substantial. In particular, we identified key classes of compounds that correlated with specific aromas: tropical volatile sulfur compounds (VSCs) containing the 3-mercaptohexyl functional group were found in a subset of varieties that produce a strong, sulfuric, petroleum-citrus aroma that was easily identified during sensory analysis. Conversely, varieties described as savoury or chemical were found to contain skatole, a compound with an extremely pungent chemical aroma.”

Skatole, one of the VSCs found in cannabis is a compound that at low levels produces a floral aroma, however, in higher doses, it smells of poo and is the main compound that produces the foul odour in mammalian faeces. 

In their summary, the researchers commented on the outcomes. “Our results yield a more complete understanding of the unique aromas that cannabis produces and help establish these non-terpenoid compounds as an important part of the phytochemistry of cannabis.”

“Furthermore, 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 results from this study add weight to results from an earlier study that identified VSCs as a driving force behind cannabis’ uniquely beautiful aroma and may encourage produces, vendors, and consumers to consider additional methods to classify the thousands of different cannabis strains* on the legal and the legacy markets. 

*In this article the author uses the more commonly known understood ‘strains’ in place of the botanically correct ‘cultivar’.