KINETICS OF ASCORBIC-ACID LOSS AND NONENZYMATIC BROWNING IN ORANGE JUICE SERUM - EXPERIMENTAL RATE CONSTANTS

The kinetics of ascorbic acid loss and nonenzymatic browning in clarified orange juice (serum) were investigated in an anaerobic environment from 70.3 to 97.6 degrees C and from 11.7 to 80.6 degrees Brix. Data were fitted to first-order kinetic models. Rate constants of ascorbic acid degradation in serum were not different from rate constants in whole juice. Activation energies were approximate to 30 kcal/mol and largely independent of solids concentration. Rate constants of browning pigment formation were 30-50% greater in serum. Activation energies were 19-25 kcal/mol and increased slightly with solids concentration.