Surfactant-ultrasound synergy for pectin from Citrus reticulata peel: Enhancing structural integrity and functional...

The structural integrity and functional characteristics of pectin are critically influenced by extraction methodologies. This study systematically compared conventional acid extraction (CAE), ultrasound-assisted acid extraction (UAE), surfactant-assisted acid extraction (SAE), and surfactant-ultrasonic-assisted acid extraction (SUAE) on the yield, structure, and functionality of pectin from Citrus reticulata peel residue (CRP). Both ultrasonic treatment and surfactants strategies improved pectin yield compared to CAE, with SUAE achieving maximum extraction efficiency (15.77% w/w). Compared to ultrasonic treatment, which selectively disrupted the homogalacturonan (HG) domain, CAE induced extensive cleavage of side chains, compromising overall structural integrity. The incorporation of surfactants in SUAE further alleviated structural damage by preserving the rhamnogalacturonan-I (RG-I) region, essential for maintaining triple-helix conformations. Pectins extracted via four methods were denoted as CAEP, UAEP, SAEP, and SUAEP, respectively. Structural analysis showed that SUAEP and UAEP maintained triple-helix conformations, while CAEP and SAEP did not. SUAEP and UAEP also exhibited superior viscosity and viscoelastic behavior, and SUAEP exhibited maximal radical scavenging rate and emulsion stability. This study advances fundamental understanding of the structure-function relationship of pectin, and provides theoretical and technical support for the high-value utilization of citrus by-products.