Extraction and stability of pigments obtained from pitaya bark flour (Hylocereus costaricensis)

Abstract

Red pitaya fruits have become a source of natural dye, because they are rich in betacyanin, a pigment that imparts a red-violet colour. However, natural dyes can be highly unstable and prone to rapid degradation. In this study, an experiment was initially carried out to determine the best extraction solution with an extraction time of 20 min for each solution at room temperature (50% methanol, water, 95% ethanol and 80% acetone), in different pH ranges (4.0 to 9.0) and wavelength (485, 535 and 700 nm), for the red pitaya bark. The stability of the pigments extracted from pitaya peel meal was analysed taking into account the best extraction solutions by spectrophotometric measurements at 15-day intervals, during a 60-day storage period, in the absence and presence of light and under different storage conditions. Pigments stored in the absence of light at freezing temperatures for less than 15 days showed least degradation. The FTIR spectrum in shows two distinct peaks at 3263.870 and 1636.807, these absorption bands are characteristic of betalain functional groups. The spectrum indicates the presence of hydroxy and amine groups as strong, broad, stretching-mode bands, appearing between 3200 cm -1 and 3600 cm -1 .

Supercritical extraction of betalains from the peel of different pitaya species

“…3(A)), is mainly composed of betalains that possibly have good stability, 33 which did not occur for the other species. For the species S. costaricensis , the extract yield positively correlated with antioxidant activity; certainly, the bioactive compounds of this species have better stability 34 . On the other hand, the antioxidant activity of this species correlated negatively with betalains but positively with the other species.…”

“…For the species S. costaricensis, the extract yield positively correlated with antioxidant activity; certainly, the bioactive compounds of this species have better stability. 34 On the other hand, the antioxidant activity of this species correlated negatively with betalains but positively with the other species. For the species S. undatus, the extraction yield correlated positively only with lightness because its solid components provide brightness, which also occurred for the species S. costaricensis.…”