Citrus flavonoid-pectin conjugates with enhanced emulsifying properties

Pectin and flavonoids are important components of citrus fruits, but the effects of flavonoid grafting on the emulsifying properties of citrus pectin remain unclear. In this study, a novel natural citrus flavonoid-pectin conjugate in citrus peel was identified through alkaline hydrolysis combined with ultra-high performance liquid chromatography. Subsequently, two major citrus flavonoids were enzymatically conjugated to citrus pectin at high grafting rates (hesperidin: 20.21%; naringin dihydrochalcone: 16.11%). The flavonoids increased pectin amphipathy while ensuring a tighter conformation and denser network structure. These structural changes reduced the interfacial tension (from 20.6 to 18.4 mN/m) and increased the adsorbed layer thickness (from 11.8 to 37.8 nm), facilitating rapid pectin anchoring at the oil-water interface. These led to smaller droplet size and better emulsion stability. Prepared flavonoid-pectin conjugates with high grafting rates exhibited better emulsifying properties than those with medium grafting rates; hesperidin-pectin conjugates were more effective than naringin dihydrochalcone-pectin conjugates. The prepared flavonoid-pectin conjugates aid in the structural identification of natural flavonoid-pectin conjugates; they also facilitate analyses of the properties of these conjugates and offer new insights into improving the functional properties of pectins used in the food industry.