Ascorbic acid oxidation in sucrose aqueous model systems at subzero temperatures.
The reduction of Tempol by ascorbic acid in concentrated sucrose solutions was measured by electron paramagnetic resonance (EPR) at temperatures ranging from 16 to -16 degrees C. This method allowed the determination of the rate constants (k) of this fast reaction, by recording the Tempol reduction as a function of time. The two reactants were initially separated and had to migrate for the reaction to occur. The experimental findings were compared with predicted values according to the equation for diffusion-controlled reaction proposed by Atkins. The experimental reaction rate constants were observed to be lower than the calculated ones. However, the experimental values were found to be controlled by the temperature and viscosity changes of the reaction media, as expected for a diffusion-controlled reaction.
Champion
Dominique
D
Laboratoire d'Ingénierie Moléculaire et Sensorielle de l'Aliment, ENSBANA, Université de Bourgogne, 21000 Dijon, France. dominique.champion@u-bourgogne.fr
Simatos
Denise
D
Kalogianni
Eleni P
EP
Cayot
Philippe
P
Le Meste
Martine
M
D001205:Ascorbic Acid / Q000737:chemistry*; D003497:Cyclic N-Oxides / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005615:Freezing; D007700:Kinetics; D010084:Oxidation-Reduction; D012996:Solutions; D013113:Spin Labels; D013395:Sucrose / Q000737:chemistry*; D013696:Temperature; D014867:Water
D003497:Cyclic N-Oxides; D012996:Solutions; D013113:Spin Labels; D014867:Water; D013395:Sucrose; D001205:Ascorbic Acid; C001803:tempol