Abstract:Differences in the physical and chemical indices, active substances, and antioxidant activities of dried pitaya peel powder during processing and storage were analyzed using various methods, including hot air, microwave, and vacuum freeze drying. The results showed that the lowest moisture content (3.76%), highest rehydration ratio (3.67), and lowest color difference (26.11) were attained via vacuum freeze-drying peel powder. Moreover, the total flavonoid (36.81 mg/g), vitamin C (42.22 mg/100 g), and anthocyanin (28.06 mg/100 g) contents, as well as the total antioxidant capacity, as measured by fluorescence recovery after photobleaching (FRAP; 1.02 Fe2+/100 g) were significantly higher in freeze-dried samples compared to other samples (P<0.05). Meanwhile, the microwave-dried pitaya peel powder had the highest total phenolic content (271.01 mg/100 g) and exhibited the best scavenging capacity for hydroxyl (82.77%), DPPH (95.10%), and ABTS+ radicals (96.86%) during storage, the vacuum-freeze-dried pitaya peel powder exhibited the lowest color difference reduction, best preservation of total flavonoids and total phenols, highest ABTS+• scavenging capacity (84.10%), and highest total antioxidant capacity, as measured by FRAP (0.84 Fe2+/100 g). Furthermore, microwave-dried powder demonstrated the highest anthocyanin and vitamin C retention ability, and the highest hydroxyl radical scavenging capacity (88.82%). In contrast, the retention of active substances in hot air-dried pitaya peel powder was inadequate. In conclusion, vacuum freeze-dried pitaya peel powder exhibited the highest quality during processing and storage. This study provides a useful reference for the production and processing of pitaya peel powder.
