Moderate-temperature hot-air drying improves color retention in sorghum seeds: Associations with lipid and flavonoid profiles.

Postharvest drying affects sorghum seed color, but the physiological and metabolic features associated with color retention remain unclear. We compared natural sun-drying (Dn), 40 °C hot-air drying (D40), and 60 °C hot-air drying (D60) using colorimetric, physiological, biochemical, and untargeted metabolomic analyses. D40 showed the best color retention, whereas Dn caused the greatest deterioration and D60 achieved the fastest dehydration. At the final moisture content, D40 had 38.42% lower malondialdehyde (MDA) content than Dn, while superoxide dismutase, peroxidase, and catalase activities were 3.84-, 3.48-, and 3.46-fold higher, respectively; D40 also showed the highest carotenoid content. Metabolomic and correlation analyses revealed distinct lipid- and flavonoid-related profiles between D40 and Dn. Phosphatidylcholine was positively associated with ΔL and negatively with MDA, while 9(10)-EpOME and leucodelphinidin were negatively associated with MDA. Together, better color retention under D40 coincided with lower lipid peroxidation, greater antioxidant enzyme activities, and distinct lipid- and flavonoid-related metabolic profiles.