title: Ultraviolet-induced oxidation of ascorbic acid in a model juice system: identification of degradation products.
abstract: Degradation products of ultraviolet (UV-C, 254 nm) treated ascorbic acid (AA) are reported. Analysis by high-performance liquid chromatography-mass spectroscopy (HPLC-MS) conducted in a 0.5% malic acid model juice system (pH 3.3) demonstrated increased degradation of AA above untreated controls with concomitant increases in dehydroascorbic acid (DHA) and 2,3-diketogulonic acid (DKGA) levels. Electron spin resonance (ESR) spectroscopy studies, conducted in phosphate buffer (pH 7.0) to increase detection sensitivity, demonstrated that ascorbyl radical (AA•) formation occurs simultaneously with AA degradation. Consistent with a previous study in which UV treatments were shown to accelerate dark storage degradation, AA• radicals continued to form for up to 200 min after an initial UV treatment. Results from this study suggest that the mechanism for UV-induced degradation is the same as the general mechanism for metal-catalyzed oxidation of AA in juice.
authors.affiliation: Department of Food Science, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
authors.forename: Rohan V
authors.initials: RV
authors.lastname: Tikekar
authors.forename: Ramaswamy C
authors.initials: RC
authors.lastname: Anantheswaran
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Elias
authors.forename: Luke F
authors.initials: LF
authors.lastname: LaBorde
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D001628:Beverages / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D010084:Oxidation-Reduction / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D001205:Ascorbic Acid