To evaluate the storage stability of betacyanins in purple
pitaya, juice was processed by straining and centrifuging
for complete removal of mucilaginous material, thus eliminating the potential betacyanin stabilising matrix effect.
Although ascorbic acid was previously reported to be absent in purple pitaya juice [10], this antioxidant was recently proven to stabilise betacyanins during thermal treatment of purple pitaya juice [15]. Therefore, samples were
stored with and without addition of 1% ascorbic acid. Since
light was earlier reported to deteriorate betacyanin stability [12–14], the effect of illumination was investigated and
compared to dark storage.