Post-harvest drying determines cannabinoid and volatile composition in pharmaceutical cannabis (Cannabis sativa)

Background Cannabis inflorescence drying is a critical post-harvest operation that directly influences product quality, phytochemical composition, and storage stability. However, limited information is available regarding the comparative effects of emerging drying technologies on the preservation of cannabinoids, terpenes, and quality attributes. Methods This study evaluated the impact of three drying methods—freeze drying, low-temperature oven drying (40 °C), and vapor pressure deficit (VPD)-controlled drying on drying kinetics, trichome integrity, colorimetric characteristics, volatile composition, and cannabinoid content of pharmaceutical-grade Cannabis sativa (‘Huckleberry’) inflorescences. Drying behavior was monitored gravimetrically, while color parameters (L*, a*, b*), volatile compounds (GC–MS), and cannabinoids (HPLC) were quantified following dehydration using gas and liquid chromatography. Data were analyzed using one-way ANOVA and Duncan’s multiple range test ( p ≤ 0.05). Results Under freeze drying the fastest dehydration was achieved, reaching the target moisture content (12%) within approximately 11 h, followed by oven drying (35 h) and VPD drying (6–7 days). Freeze drying provided superior preservation of visual quality, maintaining green coloration, high lightness, and intact trichome morphology, whereas oven drying induced the greatest pigment degradation and structural alterations. Volatile analysis revealed a terpene-rich profile dominated by monoterpene hydrocarbons, with drying method significantly influencing terpene composition and essential oil retention. VPD drying preserved the highest essential oil yield and most closely maintained the native aromatic profile, while freeze drying favored sesquiterpene preservation but resulted in substantial losses of volatile monoterpenes. In contrast, cannabinoid composition remained comparatively stable across drying treatments, with tetrahydrocannabinolic acid remaining the predominant cannabinoid and only minor decarboxylation occurring during the dehydration process. Conclusions These findings demonstrate that drying methodology exerts a much greater influence on terpene composition than on cannabinoid content. While freeze drying maximized drying efficiency and visual preservation, VPD-controlled drying resulted in the best overall balance between phytochemical retention and product quality, highlighting its potential as a post-harvest strategy for pharmaceutical cannabis production.