EFFECT OF SUCROSE ON OXYGEN-UPTAKE OF ASCORBIC-ACID IN A CLOSED AQUEOUS SYSTEM

The effect of sucrose on the oxygen uptake kinetics of ascorbic acid (A) in a closed aqueous system was studied at different temperatures (26.5, 30, and 33-degrees-C) and pH levels (3.0-5.0). The reactions generally followed a pseudo-first-order reaction with respect to dissolved oxygen. The activation energy of A oxidation in sucrose solutions was greater than that in solutions containing no sucrose at all pH levels. Approximately 1 mol of oxygen was used per mole of A at the early stage of the noncatalyzed oxidation of A in various solutions. Two effects of sucrose on the A oxidation in the closed homogeneous system were suggested. First, a pH-independent physical hindrance effect retarded A oxidation and, second, a pH-dependent catalytic effect accelerated oxidation due to metal impurities found even in analytical grade sucrose.