Abstract
Riboflavin converts into lumiflavin when irradiated in alkaline solution, but when fructose is present it also changes to leucoflavin in the same time. As a result, the formation of lumiflavin is low because leucoflavin is not photolysed in this condition. Aeration at the time of irradiation prevents the formation of leucoflavin, and then conversion to lumiflavin takes place as in the ordinary case. Since some natural sources such as fruit juices, the riboflavin content of which should be determined, contain considerable amount of fructose, the authors recommend an aeration at the stage of photolysis in the normal "lumiflavin method" for the estimation of riboflavin.
