The influence of drying methods on the physicochemical, functional, and antioxidant properties of passion fruit peel

Abstract

Objective: This study aimed to investigate the effects of drying methods on passion fruit peels. Methods: Passion fruit peels were treated with microwave vacuum freeze-drying, vacuum freeze-drying, heat pump drying, and far-infrared radiation drying. The drying characteristics, rehydration ratio, color difference, dietary fiber, functional properties, microstructure, total phenolic content, total flavonoid content, and antioxidant properties were measured and determined respectively. Results: Heat pump-dried passion fruit peels had poor rehydration ratio and functional properties. Microwave vacuum freeze drying reduced the drying time by 53% when compared tp far-infrared radiation drying, and the microwave vacuum freeze-dried treated passion fruit peels had a higher rehydration ratio (7.45), total phenolic content (13.45 mg GAE/g DW) and antioxidant activity (DPPH was 38.53%, FRAP was 1.14 mmol/L). Additionally, the passion fruit peels were vacuum freeze-dried with treatment to increase their water holding capacity [(21.64±0.21) g/g], oil holding capacity [(6.09±0.71) g/g], swelling [(25.00±1.00) g/g], and total flavonoid content (7.84 mg RT/g DW). Different drying techniques led to higher rehydration ratios, and they also significantly differed (P＜0.05) in terms of dietary fiber, functional properties, total phenolic content, total flavonoid content and antioxidant activity of the peels. Conclusion: The quality of passion fruit peel can be greatly affected by the drying process, and microwave vacuum freeze-drying is the most preferred technique.

Keywords

• passion fruit peel powder
• microwave vacuum freeze-drying
• vacuum freeze-drying
• heat pump drying
• far-infrared radiation drying
• physicochemical properties
• antioxidant activity