Cold plasma pretreatment: A novel approach to improve drying characteristics and terpene retention of cannabis (Cannabis sativa L.)

The cannabis industry has been employing low-temperature hang drying of cannabis inflorescences, which is slow and has several challenges, such as nonuniform drying and susceptibility to microbial contamination. Alternatively, high-temperature drying techniques are faster but result in the loss of valuable volatile compounds. Cold plasma (CP) technology, a novel and environmentally friendly approach, may be used to enhance drying rates while preserving the phytochemicals in food and biological products. This study investigates the application of CP treatment on undried recreational cannabis inflorescence samples at three plasma jet power levels (300 W, 350 W, and 400 W) with exposure times of 20, 30, and 40 s. The cannabis was then dried under controlled environmental conditions of 25°C and 50% relative humidity. The effects of CP pretreatment were compared with untreated samples in terms of drying characteristics, energy consumption, and chemical composition. The findings revealed that untreated cannabis samples reached an equilibrium moisture content (EMC) of approximately 16% in 1260 min. In contrast, CP-pretreated samples achieved lower EMCs of 10-14% within a substantially shorter drying time of 690-840 min. CP pretreatment also improved effective moisture diffusivity by 35-60% and increased drying energy efficiency by 50-80%. Higher CP power and extended exposure times facilitated cannabinoid decarboxylation, resulting in increased tetrahydrocannabinol (THC) levels and reduced tetrahydrocannabinolic acid (THCA), without significantly reducing the total THC content (27.45% in untreated samples versus 25.82-28.36% in CP-pretreated samples). Furthermore, CP treatment demonstrated excellent preservation of terpenes in dried cannabis inflorescences, resulting in around 96% retention of total terpenes with 400 W and 30 s CP-treatment and over 90% retention with all 300 W treatments compared to untreated samples. Overall, this study highlights cold plasma pretreatment as a promising technique for the cannabis industry, enhancing the drying process while maintaining high product quality, especially in terms of terpene content.