The highest betacyanin content was observed when 0.25 % (w/w) ascorbic acid was added to red-fleshed dragon fruit juice and the juice was adjusted to pH 4 and pasteurized at 65°C for 30 min. Betacyanin juice was found to deteriorate at the agitation speed of 220 rpm. The addition of 0.25 % (w/w) ascorbic acid helped to stabilize betacyanin in both juice and concentrate stored under agitated or non-agitated conditions. Light was also found to degrade betacyanin. In juice samples, dark storage resulted in higher betacyanin content. There was no difference in betacyanin content of concentrate samples stored in dark or light. The addition of 0.25 % (w/w) ascorbic acid shows a stabilizing effect on betacyanin of concentrate samples that were stored in light.