We previously explored citrus oil emulsion stabilized by citrus pectin. In this report, we characterized key parameters of the citrus pectin mesoscopic structure and their effect on emulsifying capacity, and explored the underlying mechanism by determining the interfacial properties, emulsifying ability, and micromorphology. To generate different mesoscopic structure, citrus pectins were hydrolyzed or regulated by pH and NaCl. Hydrolysis decreased the size of citrus pectin mesoscopic structure with constant compactness, leading to superior interfacial properties but inferior emulsifying ability. In contrast, pH and NaCl regulation decreased the mesoscopic structure size and increased the compactness, and pH and NaCl-regulated citrus pectin formed a compact absorbed layer at the interface to resist droplet coalescence/flocculation during homogenization. Our results support the importance of compactness of the citrus pectin mesoscopic structure on emulsifying capacity. This study increased our understanding on the relationship between the mesoscopic structures of polysaccharide emulsifier and emulsifying ability. (C) 2020 Elsevier Inc. All rights reserved.