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.
Keywords:
peel; pigments; natural dyes; betacyanin
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