In the field of medicine, including nutraceuticals and pharmaceuticals, extracting the most bioactive compounds possible from the material you are working with is important for several reasons. If only there was a way to increase your extraction yield using the same amount of raw material you normally use for extraction. Well, there just might be a way to do that, and it may also reduce the total time it takes for extraction.
Researchers recently considered how grinding biomass affects the extraction of bioactive compounds from plant material, and they reported some interesting results. Their study analyzed two different plant materials for extraction. These were the New Zealand manuka leaves of Leptospermum scoparium (tea tree) as well as Stevia rebaudiana (stevia) leaves. Each of the plants was ground into particle sizes between 68 μm to 1400 μm, and their extraction results were then compared against each other as well as non-ground material. 
The extraction of the manuka biomass was “processed using n-hexane extraction for 0–60 min” at 25º C, and the stevia leaf biomass was processed using hot water extraction (90° C, 1 h) and ultrasound thermal assisted adiabatic extraction (20 kHz, heated to 88º C over 10 minutes). Overall, “as particle size was reduced, the extraction of bioactives increased.” The Manuka leaf terpenoids specifically were noted to be most “easily extracted by decreasing the particle size to 68–200 µm,” and a particle size of 200 µm was ideal to shorten the extraction time of steviol from the stevia leaves. Most extraction of fine powders occurred within a few seconds, illustrating that grinding releases bioactive compounds. 
Knowing that grinding biomass can increase yield and speed up extraction time makes understanding the importance of biomaterial particle size critical to extractors. Whether you’re extracting cannabinoids or terpenes from cannabis, or terpenes and essential oils from plants like manuka, or even steviol glycosides from stevia, the particle size of the biomaterial is going to affect the outcome of your final product.
- Alsaud N., et al. Insight into the influence of grinding on the extraction efficiency of selected bioactive compounds from various plant leaves. Applied Sciences. 2020;10(18):6362. Times Cited: n/a; Journal Impact Factor: 2.474