The Influence of Pre-Harvest LEDs on Phytochemical Constituents and Antioxidant Activity of Microgreens during Short-Term Storage

This study aims to evaluate the influence of the pre-harvest light-emitting diode (LED) spectrum on the metabolic indices in microgreens during post-harvest storage. Broccoli 'Micro Green' and kale 'Dwarf Blue Green' microgreens were cultivated in a growth chamber under the photosynthetic photon flux density (PPFD) of 200 mu mol m(-2) s(-1) provided by violet (V, 405 nm), blue (B, 447 nm), green (G, 520 nm), and red (R-638, R-665, R-638 nm and 665 nm, or both, respectively) LEDs in combinations of BR638, BR665, BR, BRV, and BRG. We evaluated the total phenolic content (TPC), total protein (TP), chlorophyll (CHL), and carotenoid (CAR) contents, and the ferric-reducing antioxidant power (FRAP) and ABTS and DPPH free radical scavenging activities at harvest and during storage at 4 degrees C for five days in the dark. The results demonstrate that the influence of preharvest LEDs on the metabolic indices varied among microgreens species and decreased consistently throughout the post-harvest period. BRV treatment led to the highest TPC, CHL, and CAR in kale, and increased the DPPH radical scavenging activity in broccoli. The TP content was the highest in kale and broccoli under BR665 and BR lights, respectively. In addition, BR light had a similar impact on the antioxidant capacity at harvest day for both microgreens species. The TPC, CHL, and CAR contents were influenced by BR665 after one day from harvest.