Abstract
This study investigates the influence of visible light wavelengths including red (620 nm), blue (450 nm), white (400–700 nm), and combined red-blue lights on bioactive compounds and γ-aminobutyric acid (GABA) content in barley sprouts. The aim was to explore how spectral light treatments can enhance functional metabolites during germination. Barley seeds were germinated in darkness for 3 days and exposed to light for 5 days. Among treatments, red light significantly promoted root elongation, elevated GABA content (up to 8.2 mg/g DW), and increased total phenolic content (TPC). It also improved antioxidant activity (DPPH and FRAP) and induced the biosynthesis of ferulic and p-coumaric acids. These results suggest that red LED light modulates photoreceptor-mediated metabolism to enhance nutritional value in barley sprouts. The findings provide a scientific basis for applying LED technologies in functional food production, sprout-based supplements, and sustainable agriculture.