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Microwave Hot Air-Drying: How it Works

The process of cannabis production ranges from growth, cultivation, and distribution. Each step plays a vital role in the overall quality of the final product, as every factor and decision will alter the course of the cannabis plant. Drying cannabis is a vital part of the cultivation process as it significantly impacts total cannabidiol retention and terpenes (Chen et al., 2021).


marijuana being dried out under a lamp
Photo by Jess Loiterton via Pexels


In a study with freeze drying and air drying as the control groups, the temperature increased to 90 degrees Celsius, and drying time reduced from 1800 minutes to 210. The researchers found that “cannabidiolic-acid conversion increased from 0.2%-14.1%, and total terpene retention decreased from 82.1%-29.9%” (Chen et al., 2021). This indicates that the cannabis drying methods and environmental conditions produce different results of terpenes and cannabidiol retention.


Cannabis Drying - The Basics

Drying cannabis must account for all factors, including moisture levels, room temperatures, microbial activity, duration, and light intensity, to preserve phytocannabinoid and terpenoid contents (Al Ubeed et al., 2022). Since cannabis is around 80% water, drying maintains its medicinal properties, potency, and taste while being able to lengthen its shelf life and control microbial growth (Al Ubeed et al., 2022).


The drying process features different stages, each with a different focus. In the beginning stages of drying cannabis, the process will “encourage the movement of the flow of moisture from the inner part to the surface, while the final stages of the drying process help with the removal of the bound water present in the material” (Al Ubeed et al., 2022).


A cannabis plant is a dry product based on its crispness and texture. Any changes to the plant’s drying conditions will reduce its quality, cause cannabinoid decarboxylation, and result in a loss of terpenes (Al Ubeed et al., 2022).

Microwave-assisted hot air drying specifically removes the moisture with the “non-ionising electromagnetic waves found between the radio and infrared wavelengths on the electromagnetic spectrum” and “is based on volumetric heating and creating a temperature gradient” (Al Ubeed et al., 2022). Microwaves that possess a frequency of 915 MHz provide a greater penetration depth and are considered best for drying cannabis plants (Al Ubeed et al., 2022).


The Benefits: Microwave-Assisted Hot Air-Drying

Microwave-assisted hot air drying quickly and efficiently preserves cannabis’ color, nutrients, and microstructure (Radoui et al., 2020). One study also found that drying with a 240-watt microwave maintained the chemical composition of fresh medicinal cannabis. This drying process holds the plant’s initial terpenes and cannabinoids before drying (Al Ubeed et al., 2022).


This method works efficiently because it provides a continuous flow of atmospheric pressure that is processed in less time and does not require stopping or restarting like other drying methods may require (Radoui et al., 2020). It also eliminates the need for additional steps in the cultivation process, including winterization and biomass decarboxylation. Removing these steps in the process means nearly half a day is saved. This drying method also produced a high extraction efficiency, with up to 95% of the cannabis biomass recoverable (Radoui et al., 2020).


The Disadvantages: Microwave-Assisted Hot Air-Drying

Although this method effectively and efficiently preserves the quality of cannabinoids and terpenes present in the plant, there are still some disadvantages to microwave-assisted hot air drying. Since such a high heat level is used during the drying process, it can only be used during the last stages and can cause the product to develop an off-flavor (Al Ubeed et al., 2022).


Microwave-assisted hot air drying is quick and effective at drying and preserving cannabis plant compounds, but it may not be the method for everyone. Are you interested in learning more about other types of cannabis drying methods? Please read our article Cannabis Drying Methods: An Overview.


Trust in Steep Hill Illinois

We are proud to be a part of a network of Steep Hill labs that have consistently used the backbone of science to help build a safe cannabis community. Whether you are interested in laboratory testing, data analysis, or consulting services, you can always rely on Steep Hill Illinois to assist you with accurate, reliable results on the latest cannabis production practices. Email us today at info@steephillil.com to get started!



References:


Al Ubeed, H. M. S., Wills, R. B. H., & Chandrapala, J. (2022, March 6). Post-harvest operations to generate high-quality medicinal cannabis products: A systemic review. Molecules (Basel, Switzerland). Retrieved January 31, 2023, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8911901/#B77-molecules-27-01719


Cannabis drying methods: An overview. Steep Hill Illinois. (2023, January 25). Retrieved January 30, 2023, from https://www.steephillil.com/post/cannabis-drying-methods-an-overview


Chen, C., Wongso, I., Putnam, D., Khir, R., & Pan, Z. (2021, September 16). Effect of hot air and infrared drying on the retention of cannabidiol and terpenes in industrial hemp (cannabis sativa L.). Industrial Crops and Products. Retrieved December 15, 2022, from https://www.sciencedirect.com/science/article/abs/pii/S0926669021008165


Radoiu, M., Kaur, H., Bakowska-Barczak, A., & Splinter, S. (2020, August 21). Microwave-assisted industrial scale cannabis extraction. MDPI. Retrieved January 31, 2023, from https://www.mdpi.com/2227-7080/8/3/45



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