Oxygen effects on nonenzymatic browning and vitamin C was investigated in commercially concentrated orange juice and reconstituted single strength orange juice and grapefruit juice. Oxygen depletion in the presence of added copper (0.02 g/kg) was twice as fast in orange juice than in grapefruit juice. Copper promoted nonenzymatic browning only in grapefruit juice and not in concentrate or single strength orange juice. No significant differences were found between nonenzymatic browning values of orange juice and concentrate under anaerobic and aerobic conditions typical for commercial aseptic packaging, indicating that oxygen was not accelerating nonenzymatic browning. Addition of copper followed by an immediate decrease in Vitamin C and its concentration was markedly 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.