Study of Using Ultrasonic Waves in the Producing Dried Dragon Fruit Peel Processes

In this study, ultrasound waves were successfully applied to the osmosis process of dried dragon fruit products. Additionally, this study was aimed at determining the suitable parameters for the process of drying dragon fruit peels. The parameters including the size of slices (2-5 cm), blanching time (10-25 min), ultrasonic time (10-25 min), ultrasonic temperature (45°C-60°C), ultrasonic power (100-250 W), and drying temperature (45°C-60°C) were fully investigated. The parameters including size of slices at 4 cm, blanching time of 20 min at 100°C, ultrasonic time of 15 minutes, ultrasonic temperature of 55°C, ultrasonic power of 100 W, and drying temperature of 55°C displayed the highest vitamin C (22.291 mg acid ascorbic/100 g), total polyphenol content (1096.948 mg GAE/100 g), reducing sugar (40.643 g/L), and total sugar (724.089 g/L). The obtained products were pink, soft, as well as harmonious between sweet and sour taste. This research contributes to diversifying products from dragon fruit in Vietnam.