Sensory evaluation, flavonol concentrations, and composition of Allium cultivars grown at different CO2 levels and planting densities

Allium species, because of their characteristic flavor and numerous health benefits, were recommended to be grown by NASA Advanced Life Support (ALS) program for the Controlled Ecological Life Support System (CELSS). The focus of this program is to find a method of providing food for long-term space missions. Plants of bulbing onion (A. cepa), bunching onion (A. fistulosum), and common chive were each planted at three planting densities (10-, 15-, and 20-mm) and grown under elevated (approx 1200 ppm) and ambient (approx 400 ppm) CO2 in an environmental growth chamber. A. cepa ‘Purplette’ had more intense sensory attributes, percentage ash, Na, and K, but had lower amounts of crude fat, Mg, Ca, and percent N. Planting density did not affect flavonol content or the composition of the plants and only affected one sensory attribute, the pungency at 63 dap. Plants grown in elevated CO2 concentrations had different amounts of ash, Ca, and K. However, differences were only found at 35 to 42 dap. The constituents that varied with age were crude fat, ash, Mg, Ca, Na, K, C, and N. Allium species, particularly A. cepa, can provide a beneficial crop for the space program.