Effects of structural and conformational characteristics of citrus pectin on its functional properties.

• Ultrasound remarkably changed the structural and conformational features of pectin. • Ultrasound reduced the rheological properties and gel-formation capacity of pectin. • Ultrasonic-treated pectins had better emulsifying properties than untreated pectin. • Functional properties of pectin were largely determined by its M w and conformation. Ultrasonic degradation has become a fascinating strategy for preparing modified pectin, contributing to the improvement of pectin's functional characteristics. In this study, the impacts of structural and conformational characteristics of original and ultrasound-treated citrus pectins on their functional properties were examined. The results showed that compared with ultrasound-treated pectins, untreated pectin presented higher rheological and gelling properties primarily attributed to its larger weight-average molecular weight (M w), degree of methoxylation, amount of neutral sugar side chains, and z -average radius of gyration, as well as the more extended flexible-chain conformation. However, the ultrasound-treated pectins had better emulsifying properties than untreated pectin in an oil-in-water emulsion system. These properties, visually suggested by morphology analysis, including enhanced emulsifying capacity, emulsifying stability, reduced mean droplet size and negatively charged zeta potential. Moreover, the M w and chain conformation of untreated and ultrasound-treated pectins played more decisive roles in their functional properties than the others. [ABSTRACT FROM AUTHOR]