The previous articles (links below) focused on different methods of extraction, and the information included there has held to be true after some more years of technology development.
This article focuses on refinement, a subset of procedures also known as winterization, distillation, centrifuge processing, and liquid-liquid extraction. With an emphasis on obtaining THC free or Isolate, and how to reduce waste, how to rely on environmentally friendly methods, and which kinds of equipment are showing the most reliability and consistency in volume of processing for the costs, especially for small to medium sized processors, in support of Hemp farmers and the greater Hemp processing community.
First of all, the initial refinement process involves removing the water-soluble particles, waxes, chlorophylls, and other unwanted parts, while restoring the integrity of the extract, increasing shelf life, and quality of the overall extract.
Some of what informs the initial refinement process is how the plant is grown, if it is oxidized or decarboxylated, and also what kinds of raw materials or products the extract is going into. As was mentioned in the previous article, CO2 extraction and some of the heating processes during ethanol extraction, can take its toll on terpenes, and introduce oxidative stress into the extract.
This causes free radical cascades from the triglycerides and fatty acid portions of the extracts. This can be resolved in a couple different ways. If the refinement process is intended to keep some of the fatty acids, especially the easy to degrade alpha-linoleic acid, a ‘bleaching’ process can be used with a bleaching clay or type of betonite clay, this restores lost electrons to the degraded lipids, and allows a longer shelf life and higher quality extract.
Another method is to use flocculants, removing or reducing the fatty acid portion altogether, the most effective way to do this is using a synthetic or bio-derived chitosan type fiber, with filtering and winterization to remove the fats and waxes altogether. Chitosan and ethanol together will naturally float to the bottom of the absolute, and are easily filtered out without causing too much strain on filters, a time limiting step. Automatic winterization equipment can be purchased, and combined with rotary evaporation or falling film type evaporators for finishing.
Distillation, another method of refinement, happens at the highest rate, and is most effective as a separative or isolation method with the highest refined oils. Cannabis in general has many, many compounds that are characteristically ‘sticky’ and difficult to separate by molecular weight, and vaporization points, so usually some similar melting point fats and waxes will evaporate with the Cannabinoids, and it is best to remove these prior to short path or molecular distillation, this is a volume rate limiting step if the laboratory is wanting to move toward refinement, THC removal, or recrystallization of the absolute into full spectrum THC free extract or isolate.
Chromatography is an interesting subject, and means the separation of a multi-part extract into layers, much like a rainbow, or when you touch wet ink to paper towel, there is a ribbon of the different molecules that travel over the paper, separating into distinct layers. This process uses many different solvents, of differing polarities to migrate the components into separate areas, on a bed, or into the different solvents, as with liquid-liquid separation.
Column chromatography, while used often as an analytical method, has been shown to create a lot of industrial waste when applied to a large-scale process, the more efficient, affordable, and environmentally friendly methods involve using multiple liquids, sometimes ionic liquids that are very new developments. The design of the different combinations of liquids can provide a large variety of functions, THC removal, production of isolate, and the isolation of the more minor compounds in Hemp, CBG, CBN, CBC, and others.
One of the benefits of complete liquid-liquid systems are that you do not have the added steps and lost yields of having to do many “washing steps” and recrystallize, filter, etc. which realistically leaves around 70% retention of initial cannabinoids, whereas the higher quality equipment boasts 95% plus retention of cannabinoids and more importantly terpenes. Another benefit is that much of the solvent is recycled and is able to be used again, and since the bed is a liquid, the high expense of throwing away chromatography silica along with high levels of solvent is also avoided. Recrystallization is done in a solvent, and uses a deep freeze, and filtration step to achieve; this step is often done after liquid-liquid extraction, but is less likely to be required when using higher quality equipment, and more technical, high volume processes.
Rien Havens, Ph.D. is the Executive Director of Amrit Labs, a Not for profit business that provides laboratory consulting, research, laboratory design, and patent development in the Industrial Hemp and sustainable manufacturing. Feel free to reach out firstname.lastname@example.org Office: 720.295.4741