OXYGEN EFFECT ON NONENZYMATIC BROWNING AND VITAMIN-C IN COMMERCIAL CITRUS JUICES AND CONCENTRATE

Oxygen effects on nonenzymatic browning and vitamin C was investigated in commercially concentrated orange juice and reconstituted single st rength orange juice and grapefruit juice Oxygen depletion in the prese nce of added copper (0.02 g/kg) was twice as fast in orange juice than in grapefruit juice Copper promoted nonenzymatic browning only in gra pefruit juice and not in concentrate or single strength orange juice. No significant differences were found between nonenzymatic browning va lues of orange juice and concentrate under anaerobic and aerobic condi tions typical for commercial aseptic packaging, indicating that oxygen was not accelerating nonenzymatic browning. Addition of copper follow ed by an immediate decrease in Vitamin C and its concentration was mar kedly affected by the catalyst. A recovery period where an increase in Vitamin C was also observed Vitamin C recovery was more prominent in grapefruit juice than in single strength or concentrate orange juice.