2019 ASHS Annual Conference

Popular among chefs as garnish greens, microgreens are also considered a valuable source of antioxidant compounds and nutrients, including minerals. Seventeen species of microgreens belonging to seven different botanical families and commonly grown for their interesting color, shape, texture, and/or flavor were selected to investigate the variation of macro- and micronutrients in the edible portion. Microgreens were grown in a greenhouse using a soilless system and a natural-fiber felt as a growing medium. A modified half-strength Hoagland solution with no microelements was prepared using deionized water and applied from seed germination until harvest. Treatments were arranged in a randomized complete block design with three replications. At harvest, conducted from 10 to 19 days after sowing depending on the species, fresh yield and shoot mean fresh weight and dry matter content were measured. Dry tissue samples were analyzed for the concentration of total nitrogen (N), NO₃-N, P, K, Ca, Mg, S, Na, Fe, Zn, Mn, Cu, and B. Significant genotypic variations were observed for all minerals measured. Total-N ranged between 212.3 and 421.3 mg 100 g^-1 fresh weight (FW) and was not correlated to NO₃-N concentration. Excluding sunflower, all other genotypes had high (1,000-2,500 mg kg^-1 FW) or very high (>2,500 mg kg^-1 FW) NO₃^- concentrations. Phosphorous concentration ranged between 28.35 and 66.05 mg 100 g^-1 FW and none of the genotypes may be considered as a good source of P. Lemon balm, beet, and amaranth had the highest concentrations of K, while sunflower, radish and kale had about one fifth of the K concentration. Amaranth was also a good source of Ca and Mg. Besides amaranth, scallion, red cabbage, and Genovese basil were good sources of Ca proving over 15% of the daily Ca requirement. The concentration of S was significantly higher in all Brassicaceae and in scallion compared to the other species. All the microgreens tested had very low Na concentration (<15 mg 100 g^-1 FW). Sunflower, scallion, and shiso had the highest concentrations of Cu and could be considered a good source of Cu. The same species and amaranth had high concentrations of Fe, while sunflower had the highest concentration of Zn; however, considering the daily recommended dietary allowance for adults, none of the species could be considered adequate dietary sources of Fe or Zn, suggesting that there is potential to fortify microgreen concentrations of essential micronutrients.