Optimization of the recovery of high-value compounds from pitaya fruit by-products using microwave-assisted extraction

- Exotic fruit by-products as a source of high-value added metabolites.
- Green microwave-extraction process towards sustainable food waste management.
- Box-Behnken design to optimize extraction yield and betacyanins' extraction.
- First identification of phenolic compounds in yellow pitaya by HPLC-DAD-ESI-MSn.
- Fifteen new compounds identified in the peels of white-fleshed red pitaya.

A green microwave-assisted extraction of high value-added compounds from exotic fruits' peels was optimized by Box-Behnken design using 3 factors: solid/solvent ratio, X1, temperature, X2, and extraction time, X3. By using Derringer's desirability function, optimum extraction yields are obtained with X1 = 1/149.95 g/mL, X2 = 72.27 °C and X3 = 39.39 min (white-fleshed red pitaya) and X1 = 1/148.96 g/mL, X2 = 72.56 °C and X3 = 5.02 min (yellow pitaya) and a maximum betacyanin content is achieved with X1 = 1/150 g/mL, X2 = 49.33 °C and X3 = 5 min. None of the factors influenced the extraction of phenolic compounds. Eighteen cinnamoyl derivatives, 17 flavonoid derivatives and 4 betacyanins were identified by HPLC-DAD-ESI/MSn, 23 and 15 new compounds being described in yellow and white-fleshed red pitayas, respectively. These results indicate that it is possible to reuse these by-products to recover compounds for food and pharmaceutical industries.