Light‐emitting diode illumination optimizes bioactive phytochemicals and sensory qualities in highland barley seedlings

BACKGROUND: Highland barley seedlings are rich in bioactive phytochemicals and are suitable for the development of functional beverages. Environmental conditions during seedling cultivation are critical, with light quality being an important factor regulating plant secondary metabolism, nutritional composition, and sensory quality. However, the effects of light-emitting diode (LED) light quality on the phytochemical profile, antioxidant capacity, and sensory properties of highland barley seedlings remain insufficiently understood. This study investigated effects of four light conditions - white, red, and blue LED light and darkness - on the overall quality of highland barley seedlings. RESULTS: Blue light significantly increased total phenolics, flavonoids, vitamin C, and individual phenolic compounds, including chlorogenic acid and proanthocyanidin B2, and resulted in the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) antioxidant activity. Red light promoted higher L* and b* values and a unique aroma, characterized by elevated levels of sulfides and terpenes as determined using an electronic nose (E-nose). Gas chromatography-mass spectrometry (GC-MS) analysis identified 34 volatile compounds, confirming these light-induced changes. White light maximized chlorophyll content, probably because of its balanced red-blue spectrum, whereas cultivation in darkness resulted in the highest free amino acid content because of altered metabolic priorities. CONCLUSION: Light quality regulation can selectively affect the amino acid and chlorophyll content, color, and aroma of highland barley seedlings, with blue light being optimal for enriching bioactive compounds and improving antioxidant capacity. These findings provide a theoretical basis for light management strategies to improve the nutritional and commercial value of highland barley seedling products. © 2026 Society of Chemical Industry.