2.6. Measurement of total betacyanin content
Total betacyanins content was determined according to the method reported by Stintzing, Schieber, and Carle (2002), whereas the maximum absorbance of betacyanins was 538 nm. The experiment was done by a spectrophotometer using diluted aqueous extracts of red pitaya using UV–Vis Spectrophotometer (Genesys 10, Thermo Scientific Co.). The total betacyanins content was defined by Eq. (2):