Nutrients in Kale and Broccoli Microgreens Studied

Microgreens, i.e., vegetable greens that are harvested very early, have become popular for enhancing the look and the nutritional content of dishes. Commonly planted varieties of microgreens include broccoli, kale, cabbage, and mustard. The fully-grown versions of these plants are rich in healthy compounds, but not much is known about the levels of these chemical components in microgreens.

Thomas T.Y. Wang, Pei Chen, Beltsville Human Nutrition Research Center, Agricultural Research Service (ARS), United States Department of Agriculture (USDA), Beltsville, MD, USA, and colleagues have studied the levels of polyphenols and glucosinolates (a source of the characteristic bitter flavor of cruciferous vegetables) in broccoli and kale microgreens. The team compared the levels in plants grown on windowsills to those raised in commercial growth chambers. They placed trays of newly planted broccoli and kale seeds either on a windowsill in natural sunlight or inside a temperature- and humidity-controlled growth chamber which is exposed to artificial sunlight for twelve hours a day. After ten days, the researchers harvested the plants and assessed the nutrient contents using ultrahigh-performance liquid chromatography high-resolution mass spectrometry (UHPLC–HRMS).

The team found that the broccoli and kale microgreens were rich in polyphenols and glucosinolates for both growth methods. However, there was considerable variability in the amounts of individual compounds when comparing the two environments. For example, the levels of certain compounds, i.e., hydroxycinnamic acid esters of flavonols, were higher in windowsill-grown microgreens. Chamber-grown plants had higher levels of some glucosinolates, i.e., 4-methoxyglucobrassicin and neoglucobrassicin. Overall, the growth environment for kale and broccoli microgreens affects the levels of individual nutrients, which could change both their flavor and potential health benefits.