Text Box: Text Box: CHEMISTRY & NUTRITION Text Box: Mechanism of Riboflavin Destruction under Light Text Box: Hyun Jung Kim and Dr. Min Text Box: Riboflavin is an essential vitamin and present in milk, eggs and meats. Riboflavin is stable during processing and storage in dark, but it is very sensitive to light. The rapid destruction of riboflavin in foods under light has significantly adverse nutritional impact and lowers the quality of foods. The mechanisms of rapid destruction of riboflavin and the protection of riboflavin under light have been extensively studied since riboflavin was discovered in 1930s. The objectives in this study were to separate and identify the compounds formed from riboflavin under light and to study the mechanisms for the formation of compounds from riboflavin to minimize the destruction of riboflavin in foods under light. The compounds formed from riboflavin in phosphate buffer under light were isolated and separated by the combination of HPLC and SPME-GC and then identified using Mass Spectrometry. Lumichrome, lumiflavin, and 2,3-butanedione formed from riboflavin under light were positively identified. The pH of riboflavin solution significantly influenced the formation of lumichrome and lumiflavin. Lumichrome was the major product under neutral or acidic pH. Lumiflavin was also formed in basic pH. 2,3-Butanedione was the major volatile compound. Lumichrome and lumiflavin were formed from unstable diradical excited triplet riboflavin by dealkylation. 2,3-Butanedione was produced from the reaction between electrophilic singlet oxygen and electron-rich riboflavin. The addition of sodium azide or ascorbic acid, which are singlet oxygen quenchers, to riboflavin solution minimized the formation of 2,3-butanedione under light. Sodium azide and ascorbic acid can protect riboflavin in foods under light.