Purple light-emitting diode (LED) lights controls chlorophyll degradation and enhances nutraceutical quality of postharvest broccoli florets

The aim of this study was to evaluate the effect of white, red, green, yellow, blue and purple LED lights on visual and nutraceutical quality of broccoli florets during storage at 20 °C for 5 days. The results showed that purple LED light exhibited the best effect on reducing yellowing and retaining chlorophyll via down-regulating expression of genes related to chlorophyll degradation, including BoSGR, BoPAO, BoNYC1 and BoRCCR. On the other hand, yellow, blue and purple LED light increased contents of total phenolic and carotenoids compared to darkness. The highest glucoraphanin content was recorded in purple LED light treated broccoli florets, which was supported by the enhanced expression levels of genes related to glucoraphanin biosynthesis. Meanwhile, purple LED light promoted myrosinase activity and its expression, and reduced ESP expression; thus enhanced sulforaphane formation. In conclusion, among all LED lights, purple LED light showed a significant positive effect considering all estimated indicators and would be useful to maintain and improve the quality of broccoli during storage at 20 °C.