Onion Bulb Source & Identity
The species is Allium cepa L., a biennial bulb vegetable of the amaryllis family (Amaryllidaceae). The part used here is the bulb. Leaves, flower stalks and seed are not used. Onion should not be confused with shallot, which belongs to the same species but forms clustered bulbs, or with garlic (Allium sativum) and the bunching onion (Allium fistulosum), which are different species with their own chemistry. Yellow, red and white onions are cultivar groups of the same species. Onion bulbs contain flavonol glycosides based on quercetin, organosulfur compounds that form when the tissue is cut, fructans and sugars. They appear as families only, since the onion extract is not sold on a quercetin or sulfur figure. Pungency and sugar content differ by cultivar, but the species and the part stay the same.












