Testing Drying Kinetic Models and the Effect of Drying on Cannabinoids of Floral Hemp (Cannabis sativa L.) in a Pilot-Scale Cabinet Dryer

Abstract Purpose Floral hemp must be dried before storage and processing. Due to a growing interest in cultivating floral hemp for cannabinoid extraction, there is a need to evaluate the drying process and determine the effect of different drying conditions on the various cannabinoids. It is also important to validate existing drying kinetic models at the pilot scale. Methods Three floral hemp cultivars (Lifter, Bubbatonic, and Quick Spectrum) were dried in a pilot-scale cabinet dryer (148 cm × 88 cm × 188 cm) at temperatures of 25 °C, 35 °C, or 45 °C, with airflow rates of 1 m s −1 or 2 m s −1 . Samples were collected at different time intervals and analyzed for moisture and cannabinoid contents. Results The drying rates at 35 °C and 45 °C were not statistically different. Drying of floral hemp from 73% moisture content (wet basis) to less than 11% took approximately 6.5 h at 45 °C and an airflow rate of 2 m s −1 . When compared to higher temperatures, increasing airflow had a significant effect on drying time at lower temperatures. The newly proposed Gaussian-based model was slightly better than the existing six thin-layer models as the adjusted coefficient of determination was 0.996 ± 0.002. Cannabinoids analysis showed that drying temperature and airflow rates did not significantly affect cannabinoid content, but longer drying times resulted in the decarboxylation of their acidic form into neutral forms and the degradation of major cannabinoids. Conclusion These results show that farmers and processors can adopt higher temperatures (45 °C) and airflow rates (2 m s −1 ) when using a pilot-scale cabinet dryer.