Live resin CBD: what fresh-plant extraction changes

Two products carry the word "live" and proceed differently. The review by Lazarjani and co-authors, published in 2021 in the Journal of Cannabis Research, describes the families of methods.

Live resin is a solvent extraction, using light hydrocarbons or supercritical CO2, applied to frozen fresh material. Live rosin, for its part, is obtained without solvent, through heat and mechanical pressure, generally from an ice-water hash. The consequence for the buyer is direct: the former calls for a residual-solvent check, the latter produces none by construction.

The review gives the technical reference points for supercritical CO2, whose critical point sits at 31.06 °C and 73.83 bar, and notes that pressurising flammable hydrocarbons carries risks, as industrial gases can introduce impurities.

A point of honesty, stated by the authors themselves: while freezing is presented as preserving volatile compounds and acidic cannabinoids, no peer-reviewed data supports the method, only industry claims. Our articles on solventless extraction and on wax-type concentrates describe the neighbouring processes.

The figure of "31% of terpenes lost in a week" circulates everywhere, attributed to a 1996 study. We could not find it in the primary source, whose public abstract contains no percentage. We will therefore not repeat it.

The usable data comes from work by Wanas and co-authors published in 2020 in Natural Product Communications, which compares the volatile oils of fresh and air-dried buds across several chemotypes. On the CBD-dominant chemotype, monoterpenes account for 58.7% of the volatile oil in fresh material against 46.5% after drying, with myrcene falling from 27.5% to 17.1%. On an intermediate chemotype, no notable change is recorded.

Two reading precautions apply. These values are relative shares of the volatile oil's composition, not absolute losses in milligrams per gram: the monoterpene share falls partly because the sesquiterpene share rises. And the effect depends on the cultivar; it is not universal.

The picture usefully thickens with a study by Birenboim and co-authors published in 2024 in the journal Plants, devoted to cultivar-adapted drying approaches. Total terpene content there increases by around 25 to 30% during drying of the THC-rich cultivar, through a concentration effect on the dry matter, with β-myrcene falling by only 3 to 20% depending on conditions. In other words, well-conducted drying is not synonymous with massive loss.

This is the most useful result for a buyer, and the least publicised. A study by Milay and co-authors published in 2020 in Frontiers in Plant Science, on optimal post-harvest storage conditions, records an average drop in terpenoid concentration of more than 50% after four months, to be compared with an average loss of 26% for phytocannabinoids after twelve months.

The authors also flag a counter-intuitive observation: despite very different volatilities, monoterpenes and sesquiterpenes follow comparable trends. Storage at 25 °C is the most unfavourable.

The practical conclusion is clear: between a poorly stored live resin extract and a conventional extract kept cool and away from light, the extraction method is not the dominant factor. Our articles on the role of terpenes detail what these molecules bring to the aromatic profile.

For a solvent-obtained extract, the certificate of analysis must include a residual-solvents line. The comparison benchmark is the ICH Q3C guideline on residual solvents, taken up in chapter 5.4 of the European Pharmacopoeia. It classes solvents into three categories: those to avoid, such as benzene, limited to 2 ppm; those to limit, such as hexane at 290 ppm; and those with low toxic potential, including ethanol, pentane and acetone, acceptable up to 5,000 ppm, i.e. 0.5%.

An observation we have seen nowhere else and which deserves saying: butane and propane, the hydrocarbons most used for this type of extraction, appear in none of the guideline's tables. There is therefore no pharmacopoeial limit to hold them against. That is precisely what makes the certificate of analysis indispensable rather than optional.

A second point of honesty: these standards govern medicines. A hemp extract sold as a consumer product in France is not a medicine, and is therefore not legally subject to them. They are a comparison benchmark that a serious producer applies voluntarily.

Whatever the method, paragraph III of article 1 of the decree of 30 December 2021 caps the Δ⁹-THC content of hemp extracts and the products that incorporate them at 0.30%. A live resin must therefore itself respect that ceiling, and not only the plant it comes from. Our CBD extracts are tested within this framework.

Does live resin contain more terpenes than a conventional extract?

No peer-reviewed study compares, on the same variety, an extract from frozen fresh material with an extract from dried material. What is documented is the decline in the monoterpene share of the volatile oil after drying on certain chemotypes. Inferring a measured superiority of the finished product would be an extrapolation.

What is the difference between live resin and live rosin?

Live resin is extracted with solvents, hydrocarbons or supercritical CO2. Live rosin is obtained without solvent, through heat and pressure. The former justifies a residual-solvent analysis; the latter generates none. Both start from frozen fresh material.

How should an extract be stored to limit terpene loss?

Cool, and away from light and air. The 2020 study by Milay and co-authors records an average terpenoid loss of more than 50% after four months, storage at 25 °C being the most unfavourable. Storage weighs more heavily on the aromatic profile than the choice of extraction method.