18C-6 |
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R. HUANG and D. B. Min. Dept. of Food Science & Technology, Ohio State Univ., 2015 Fyffe Ct., 110 Parker Food Science Bldg., Columbus, OH 43210-1007 Riboflavin is an effective photosensitizer in food systems. However, there is no report on the effects of decomposition products of riboflavin on the photosensitized oxidation of foods. The objectives of this research were to determine the major photo degradation product of riboflavin under light and to study their effects on the photosensitized oxidation of foods. Riboflavin aqueous solution (100 mM) was stored under light or in dark for 48 hours. Riboflavin degradation was only observed when the sample was stored under light. The major degradation product was identified as lumichrome by a combination of d LC/MS and HPLC retention time. Soymilk was supplemented with either 100 mM of riboflavin or 100 mM of lumichrome. The 10 mL bottles with 2 mL soymilk were air-tightly sealed and stored under light or in dark for 48 hours. Headspace oxygen and headspace total volatiles were analyzed by gas chromatography. The head space oxygen contents of soymilk samples with or without added riboflavin or lumichrome stored in the dark were essentially the same of 20.10% without change. The headspace oxygen contents of soymilks supplemented with riboflavin or lumichrome under light 18.27% and 18.47%, respectively. Both are significantly lower than the soymilk without the riboflavin or lumichrome supplementation (20.10%). SPME/GC analysis indicated that soymilk supplemented with riboflavin or lumichrome produced much more headspace total volatile than the soymilk without the supplement under light. While the same samples were stored in dark, the levels of total headspace volatiles were the similar. Lumichrome is also an effective photosensitizer in foods. Riboflavin should be protected from light to prevent the formation of lumichrome. The lumichrome is a strong photosensitizer for singlet oxygen which oxidizes food components effectively.
Session 18C, Food Chemistry: Food composition, analysis and volatiles
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |