Evolution of temporal dynamic of volatile organic compounds (VOCs) and odors of hemp stem during field retting

Abstract

Main conclusion New non-destructive approach to evaluate the retting process was investigated. Increase of retting duration led to a decrease of VOCs emitted by plants and change of color and plant odor. The variation of VOCs and odor could be used as indicators for the degree of retting.

Cannabis Cultivation Facilities: A Review of Their Air Quality Impacts from the Occupational to Community Scale

“…Rice and Koziel , sampled cannabis headspace and determined that VOCs with low concentrations but high odorous character (i.e., low odor thresholds) are mostly responsible for the odor. Even when GC-MS or other techniques are not available, olfactometry analysis can still be used to generate quantitative estimates of the odor concentration through the Odor Units (OU), which quantifies the number of dilutions with fresh air necessary for 50% of a group of trained panelists to stop detecting the odor. When odor concentration (OU·m –3 ) is multiplied by the flow rate of emissions (m 3 s –1 ), the corresponding rate of odor emission in (OU·s –1 ) is useful for dispersion models and regulatory purposes.…”

“…For example, β-myrcene ranged from 27% to 43% (30 day growth) and from 18% to 60% (46 day growth). Terpenes were also the most abundant chemical family in BVOC measured from hemp stems harvested after 15 weeks (end of flowering), accounting for 60% of total composition . Other groups included alcohols at 17%, aldehydes at 13%, and ethers at 5% .…”

“…The panel found the odors very unacceptable (−4.3 harvested at seed maturity and −4.9 after flowering on a 0 to −5 scale) and of average intensity (3.3 harvested at seed maturity and 3.5 after flowering on a 0 to 5 scale). “Dry/Green plants smell” were the descriptors most used, followed by “soft”, “fermented”, and “humus” …”

“…Terpenes were also the most abundant chemical family in BVOC measured from hemp stems harvested after 15 weeks (end of flowering), accounting for 60% of total composition. 40 Other groups included alcohols at 17%, aldehydes at 13%, and ethers at 5%. 40 After 20 weeks (seed maturity), the emission strength reduced by half.…”

Extraction of cellulose fibers from flax and hemp: a review

“…However, advances in microbiological and biochemical sciences, namely in metagenomics, metatransciptomics and metaproteomics, are making it possible to investigate and analyze these correlations to improve understanding and thereby achieve greater control over the retting process (Djemiel et al 2020). Other attempts to chart the course of retting and obtain consistent results, include measurements of color change in the plant mass, measuring the emanation of volatile organic compounds and odor, analyzing changes in chemical composition, or subjecting the plant mass to standardized peeling tests (Bleuze et al 2020;Mazian et al 2019;Mooney et al 2001;Réquilé et al 2018b). Nonetheless, the practice commonly followed at present is for farmers to empirically judge the adequacy of retting by sight, touch, and smell.…”