Effects of different drying methods on drying characteristics and quality of chili peppers (Capsicum annuum L.): Insights from changes in carotenoid and alkaloid secondary metabolites.

This study evaluated the effects of sun drying (SD), heat pump drying (HPD), far-infrared drying (FIRD), and combined FIR with HPD (FIR-HPD) on drying kinetics and quality attributes of chili peppers, using metabolomics to profile changes in carotenoids and alkaloids. Mechanical drying accelerated the drying rate by 56.8-90.3% compared to SD. Color retention was superior in peppers dried at 45 °C and 55 °C, whereas SD caused color fading. Ascorbic acid was better preserved in SD and 45 °C-dried samples, while total phenolics, antioxidant capacity, and carotenoids decreased with rising temperature. Capsaicin was lowest in SD peppers. Among 44 identified carotenoids, degradation was more severe in SD than in FIR-HPD, with zeaxanthin, capsanthin, and capsorubin as key metabolites in the enriched carotenoid biosynthesis pathway. Additionally, 132 differential alkaloids were screened from 236 identified, mainly enriched in tryptophan metabolism. Overall, FIR-HPD improved drying efficiency and better preserved bioactive compounds in dried chili peppers.