Comparative Study of Effects of Acid–Ultrasound and Cold Plasma Treatments on Structural and Emulsifying Properties of Pomelo Albedo Fiber

Abstract

Pomelo albedo is a fiber-rich by-product that may be used as a functional food ingredient, but its native compact structure and high insoluble fiber content can limit its performance in emulsionbased systems. This work compares acid-ultrasound and cold plasma treatments as nonthermal modification strategies to improve the structural and emulsifying properties of pomelo fiber (PF). PF was modified using acid-ultrasound (UL) and cold plasma (CP) treatments for 10 (CP10), 20 (CP20), and 30 (CP30) min. FTIR and SEM were used to observe structural changes, while emulsifying performance was evaluated using the emulsifying activity index (EAI) and the emulsion stability index (ESI). SEM revealed disrupted fibrous surfaces and increased porosity, while FTIR indicated changes in hydrogen-bonding interactions, suggesting shifts in surface structure and morphology after treatment. Acid-ultrasound treatment showed the highest EAI (9.30 m 2 /g), compared with 4.35 m 2 /g in PF and 4.81– 5.05 m 2 /g in cold plasma treatments (p < 0.05); ESI showed the same trend. While cold plasma showed a treatment-time-dependent pattern, with CP20 maintaining relatively the best stability, it subsequently decreased in CP30. These findings provide a basis for exploring the more robust mechanistic possibilities of acidultrasound, which demonstrated potential as a modification approach to improve PF functionality in an emulsion system.