Effects of Water Activity, Light Intensity and Physical Structure of Food on the Kinetics of Riboflavin Photodegradation

The kinetics of light‐induced riboflavin degradation were evaluated in elbow macaroni, particulate macaroni, nonfat dried milk, skim milk and a buffered solution of riboflavin. A first order degradative mechanism was observed in liquid systems, while a two‐phased mechanism was observed in dry food systems. Light intensities of 25, 50 or 100 ft‐c showed no significant differences in effect on the rate of riboflavin loss in elbow macaroni; however, a very dim light showed only a single‐phased first order rate of loss. In elbow macaroni exposed to a broad range of water activities the degradation of riboflavin increased at elevated relative humidities. Lumichrome was determined to have limited use as a quantitative indicator of riboflavin loss, but could be used as a qualitative indicator of riboflavin degradation.