Effect of light on betacyanin content was conducted according to
a method modified from Herbach et al. (2007). Juice or concentrate
samples were pretreated with the optimized processing
conditions for red-fleshed dragon fruit juice (0.25 % ascorbic
acid, adjusted to pH 4 and pasteurized at 65 °C for 30min). Juice
or concentrate sample (10 mL) was stored in clear 10.5mL vials. Samples that were stored under light conditions were placed in a laminar flow cabinet (model AHC-4D1, Esco, Malaysia) with a built-in warm white 5000 k electronically ballasted lighting. Samples stored in the dark were wrapped in aluminum foil and kept in the dark. All the samples were stored at room temperature. Samples were taken out weekly from the same vial for a total of 5 weeks for analysis of betacyanin content.