Systematic profiling of aroma and quality in UV-B treated grapes across fruit development stages

Light is an essential environmental factor regulating plant growth and development. Radiation with distinct wavelengths and light composition can induce quantitative and qualitative variations in plant phenolics and aromatic compounds. However, the underlying regulatory by ultraviolet radiation B (UV-B) affects grape berries remain poorly understood, especially from young fruit stage to ripening. In this study, light-emitting diodes (LEDs) were employed to investigate the effects of UV-B radiation on grape berries cross the whole grape development. The results demonstrated that UV-B treatment significantly increased the total soluble solids and soluble sugars (sucrose, glucose and fructose) contents while accelerating the degradation of organic acids. Additionally, this treatment increased the contents of anthocyanins, flavanols, total phenols and flavonoids, with a more pronounced elevation observed for certain monomeric phenols. Concurrently, significant differences in free and bound forms of aroma compounds were observed, especially the accumulation of aldehydes, ketones, esters, and terpenes. Principal component analysis (PCA) indicated that UV-B light was the overall promoter of grape quality. This study confirms that UV-B is a crucial environmental factor for fruit development, and provides novel insights into enhancing the accumulation of metabolites and aromas in plant-derived foods via UV-B. It further highlights the unique regulatory role of UV-B in modulating light quality, and suggests the potential application of this technique to improve the nutraceutical value and quality traits of grape berries.