The effect of supplemental LED lighting in the range of UV, blue, and red wavelengths at different ratios on the accumulation of phenolic compounds in pak choi and swiss chard

• Published in: Food research international Vol. 200; p. 115438
• Main Authors: Wessler, Caspar-Friedrich, Weiland, Martin, Einfeldt, Sven, Wiesner-Reinhold, Melanie, Schreiner, Monika, Neugart, Susanne
• Format: Journal Article
• Language: English
• Published: Canada Elsevier Ltd 01.01.2025
• Subjects: Anthocyanins; antioxidant activity; Antioxidants - analysis; Apigenin - analysis; Beta vulgaris subsp. vulgaris; Betalains; Brassica rapa - chemistry; Brassica rapa - radiation effects; Brassica rapa subsp. chinensis; chard; Chromatography, High Pressure Liquid; exposure duration; Flavonoid glycosides; food research; glycosides; greenhouses; health promotion; Hydroxycinnamic acid esters; irradiation; kaempferol; Kaempferols - analysis; leaf lettuce; Light; Light emitting diodes; lighting; Phenols - analysis; Photosynthetically active radiation; quercetin; Quercetin - analysis; rhubarb; species; Ultraviolet Rays; Ultraviolet-B radiation; Hydroxycinnamic acid esters; Photosynthetically active radiation; Anthocyanins; Light emitting diodes; Betalains; Flavonoid glycosides; Ultraviolet-B radiation
• ISSN: 0963-9969; 1873-7145; 1873-7145
• DOI: 10.1016/j.foodres.2024.115438

[Display omitted] •UV radiation as a new technique to improve food quality in greenhouse production.•Pak choi has a higher number and concentration of phenolic compounds than swiss chard.•Kaempferol glycosides in pak choi increased due to irradiation with UV-B.•In swiss chard the flavonoid concentration fluctuated strongly. Phenolic compounds are known for their health-promoting effects on humans. Pak choi (Brassica rapa ssp. chinensis) and Swiss chard (Beta vulgaris subsp. vulgaris) are used here as model plants, as they are eaten raw as baby leaf lettuce and differ in their phenolic compound profile while showing similar morphology. In a greenhouse an artificial light source with UV-B (215 mW m−2), blue (104 μmol m−2 s−1) and red (245 μmol m−2 s−1) LEDs was implemented to increase phenolic compounds during the last days before harvest. Pak choi shows an increase or trend towards an increase in the monoacylated triglycosides of kaempferol and quercetin after 4 days of irradiation for 4 h each. For example kaempferol-3-caffeoyl-sophoroside-7-glucoside was increased at low PAR values in the third run and red-dominated light treatment by up to 120 %. In addition, it was observed that the red variety ‘Amur’ has higher concentrations of quercetin glycosides which were increased often. In swiss chard, on the other hand, there was only a sporadic increase in vitexin glycosides. Despite very different concentrations in some samples, 2″-glucosyl-vitexin and 2″-glucosyl-6″-malonyl-vitexin showed significant increases of up to 350 % in the two chard varieties Lukullus and Rhubarb chard. The results suggest that the exposure time or intensity of UV-B radiation needs to be optimized for each species and has not yet consistently led to an increase but trends in phenolic compounds and in antioxidant activity in this study.