Stabilization of betalains from the peel of red dragon fruit [Hylocereus polyrhizus (Weber) Britton & Rose] through biopolymeric encapsulation

The betalain contents of red dragon fruit [Hylocereus polyrhizus (Weber) Britton & Rose], as determined by spectrophotometry, were 30.18 ± 3.01 mg per 100 g of fresh peel and 42.71 ± 2.48 mg per 100 g of fresh pulp. Thin-layer chromatographic analysis showed betacyanins as the only type of betalain component in the peel and pulp. Betalain extract was encapsulated, employing emulsification technique, in three matrices: maltodextrin (3:1 wall-to-core ratio); maltodextrin-gum Arabic and maltodextrin-dragon fruit peel pectin, both using a 4:1 wall-to-core ratio. Optical microscopy imaging showed that matrix-type and shard-like microparticles were obtained. Encapsulation of betalains promoted significantly higher stability (P < 0.05) at different storage conditions: 4 °C and room temperature (27 °C) with and without light. Furthermore, encapsulated betalains had greater percent retention at high temperatures (80 °C and 100 °C), under various pH levels (1.2, 3.6, 5.6 and 7.4) and water activity (0.089 and 0.898) compared with the non-encapsulated betalain extract. In a model drink system, maltodextrin-betalain (MB) microparticles had higher betalain retention (84.22 ± 1.24%) compared with the non-encapsulated betalain extract (70.28 ± 0.87%) after a 21-d storage period.