Optimization of betalain extraction from dragon fruit (Hylocereus undatus) peel and effect of pH on its properties

Dragon fruit peels are wastes produced in the food industry and contain abundant phytochemicals. In this study, betalain extraction from dragon fruit peels was optimized using water as a safe and environment-friendly solvent. The Box-Behnken design was used to investigate the effects of different pH (2.0-6.0), temperatures (30-60 degrees C), times (10-60 min), and solid-to-liquid ratios (1:15-1:40 by weight) on betalain extraction from dragon fruit peels. The betalain extracted under the optimized conditions was then studied for its properties across a wide pH range of 2.0 to 13.0. The results showed that the solid-to-liquid ratio had the most significant effect on betacyanin extraction as the major component of betalain in dragon fruit peels. The optimal extraction conditions were determined to be a pH of 3.6, temperature of 30 degrees C, extraction time of 10 min, and a solid-to-liquid ratio of 1:15. The expected betacyanin content under these conditions is 72.37 mg/L. A significant change in the CIELAB parameter of the extracted betalain was observed, with marked differences in the L*, a*, and b* values as the pH increased. This color change may be attributed to the degradation of betacyanin into betalamic acid. This study demonstrated the potential of a safe and eco-friendly process for extracting the natural pigment betacyanin from this agricultural waste material and the potential use of betalain in pH-dependent products.