Sustainable valorization of pitaya (Hylocereus spp.) peel in a semi-continuous high-pressure hydrothermal process to recover value-added products

This study evaluated the use of a semi-continuous high-pressure hydrothermal process for the recovery of valueadded products from pitaya peel. The process was carried out at 15 MPa, a water flow rate of 2 mL/min, a solvent-to-feed ratio of 60 g water/g pitaya peel, and temperatures ranging from 40 to 210 degrees C. The results show that extraction temperatures (between 40 and 80 degrees C) promoted the recovery of betacyanin (1.52 mg/g), malic acid (25.6 mg/g), and citric acid (25.98 mg/g). The major phenolic compounds obtained were p-coumaric acid (144.63 & PLUSMN; 0.42 & mu;g/g), protocatechuic acid (91.43 & PLUSMN; 0.32 & mu;g/g), and piperonylic acid (74.2 & PLUSMN; 0.31 & mu;g/g). The hydrolysis temperatures (between 150 and 210 degrees C) could produce sugars (18.09 mg/g). However, the hydrolysis process at temperatures above 180 degrees C generated Maillard reaction products, which increased the total phenolic compounds and antioxidant activity of the hydrolysates. Finally, the use of semi-continuous high-pressure hydrothermal process can be a sustainable and promising approach for the recovery of value-added compounds from pitaya peel, advocating a circular economy approach in the agri-food industry.