Brassica vegetables are widely recognized as nutrient-dense “superfoods”, yet they rapidly lose market value during postharvest storage due to weight loss, yellowing, and nutrient degradation. This study systematically investigated the impact of postharvest photosynthetically active radiation (PAR) and ultraviolet-B (UV-B) on secondary metabolites, antioxidant enzymes and gene expression in broccoli and red cabbage during six-day cold storage. Light treatments induced species-dependent metabolic reprogramming that developed dynamically during the storage period. Broccoli exhibited greater sensitivity to light-induced weight and chlorophylls loss, particularly under UV-B alone and combined with PAR. PAR + UV-B induced a rapid activation of the phenylpropanoid pathway, enhancing flavonoid biosynthesis and antioxidant activity, with peak at mid-to-late storage. In contrast, red cabbage showed greater structural and compositional stability, maintaining higher initial levels of flavonol glycosides and exhibiting more sustained antioxidant and enzymatic stability, with more temporally coordinated response to light. These findings demonstrate that light quality critically shapes postharvest metabolic response, especially induces increases of 21–77% in flavonol glycosides and 7–20% in antioxidant activity. A single PAR + UV-B exposure can pre-condition broccoli to achieve peak antioxidant potential during storage, whereas energy-efficient PAR alone is sufficient to preserve the superior nutritional status of red cabbage. Tailoring light spectra and application timing provides a scalable, chemical-free approach to maintain color, nutritional quality, and functional value of Brassica vegetables during refrigerated distribution.
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