Physicochemical and emulsifying properties of orange fibers stabilized oil-in-water emulsions

The present work aimed to evaluate the physical and techno-functional property and microstructure of freeze-dried orange pulp and peel powders modified by high-pressure homogenization (HPH) treatment, and their emulsifying properties of oil-in-water emulsions treated with HPH. For orange pulp and peel powders, HPH pre-treatment was found to significantly reduce bulk density and increase the water and oil holding capacity (P < 0.05) of orange pulp and peel powders, and the particles appeared to have flake-like shape. When orange-pulp and peel dispersions were subjected to HPH treatment, all samples showed significant decreases in particle size and increases in ζ-potential (P < 0.05), and could maintain higher stability with extended storage time. Furthermore, Confocal Laser Scanning Microscopy (CLSM) also revealed that emulsion destabilization occurred with increased storage time due to oil-droplet aggregation and coalescence. The results indicated that emulsion stability was improved by HPH treatments, probably due to a steric or electrostatic repulsion against flocculation or coalescence of oil droplets, and orange fibers, particularly orange pulp are suitable feedstock as natural emulsifiers.