The Effect of Light Intensity during Cultivation and Postharvest Storage on Mustard and Kale Microgreen Quality

Microgreens are vegetable greens that are harvested early while they are still immature and have just developed cotyledons. One of the disadvantages and a challenge in production is that they exhibit a short shelf life and may be damaged easily. In seeking to prolong the shelf life, some pre- and postharvest interventions have been investigated. Here, kale and mustard microgreens were grown in a controlled-environment walk-in chamber at +21/17 °C, with ~65% relative air humidity, while maintaining the spectral composition of deep red 61%, blue 20%, white 15%, and far red 4% (150, 200, and 250 µmol m^-2 s^-1 photosynthetic photon flux density (PPFD)). Both microgreens seemed to exhibit specific and species-dependent responses. Higher PPFD during growth and storage in light conditions resulted in increased contents of TPC in both microgreens on D₅. Additionally, 150 and 250 PPFD irradiation affected the α-tocopherol content by increasing it during postharvest storage in kale. On D₀ 150 for kale and 200 PPFD for mustard microgreens, β-carotene content increased. D₅ for kale showed insignificant differences, while mustard responded with the highest β-carotene content, under 150 PPFD. Our findings suggest that both microgreens show beneficial outcomes when stored in light compared to dark and that mild photostress is a promising tool for nutritional value improvement and shelf-life prolongation.