PROBLEM TO BE SOLVED: To provide a method for treating onions by which the content of Quercetin or glycoside thereof (quercetins) in the onions increases: and to provide the onions treated by the method. SOLUTION: The method for treating the onions comprises: applying fertilizer having 5-aminolevulinic acids as active ingredients to the onions; cultivating the onions followed by harvesting the onions; and irradiating with ultraviolet rays the harvested onions. In the method, it is preferable that the amount of the fertilizer to be applied is such as to exert no influence on the content of the quercetins falling in the onions before irradiation with the ultraviolet ray, application of the fertilizer starts from 30-90 days before harvesting the onions, the wavelength of the ultraviolet ray is 315-380 nm, and a period for irradiating the ultraviolet rays is 1-14 days. The onions is treated by the method for treating the onions. COPYRIGHT: (C)2012,JPO&INPIT
