Valorization of the Peel of Pitaya’s Fruit ( Hylocereus polyrhizus ) Producing Betalain-Rich Freeze-Dried Microparticles

The demand for natural dyes of plant origin has increased in recent years. The peel of pitaya (dragon fruit— Hylocereus polyrhizus ) is a food by-product that has high concentrations of betalains and, therefore, can be a source of extraction of this pigment. Because they are very unstable, the association of betalains with protective materials tends to be interesting. The aim of this study was to produce microparticles of betalains extracted from the pitaya peel via freeze-drying, characterize the particles and apply the best formulation in a soy-based drink. Different formulations containing an extract rich in betalains and different carrier agents (maltodextrin, soy protein and xanthan gum) were produced, subjected to rheological analysis and subsequently freeze-drying. The microparticles containing 30% w/w of maltodextrin showed better physical–chemical, thermal, morphological properties and high reconstitution capacity. This treatment showed high thermal stability by thermogravimetric analysis and low moisture contents (2.31 ± 0.07%), water activity (0.29 ± 0.01), bulk density (0.35 ± 0.03 g/cm 3 ) and hygroscopicity (5.26 ± 0.03%), a very attractive reddish color was also seen. A high reconstitution capacity of this treatment was also verified, since the wettability and solubility were high (9.00 ± 0.60 s and 84.34 ± 0.03%, respectively). These microparticles were applied in soy beverages stored at different temperatures, refrigeration and mainly freezing delayed the degradation of this pigment. In this way, it was observed that the powdered microparticles of the residue help in the stability of the betalains are a good alternative to dyes of animal origin. Graphical Abstract