Manosonication assisted extraction and characterization of pectin from different citrus peel wastes

The rhamnogalacturonan I (RG-I) region of pectin revealed functional benefits and novel gel applications. This work investigated the applicability of manosonication extraction (MSE) for RG-I enriched pectin recovery from different citrus peel wastes, including Eureka lemon (LEPp), Guanxi pomelo (POPp), navel orange (ORPp), and grapefruit peels (GRPp). The physicochemical, structural, and macromolecular features of the extractions were systematically evaluated and compared to commercial citrus peel pectin (CCPp). The yields of LEPp (21.76%), POPp (20.17%), and ORPp (20.81%) were significantly higher than GRPp (17.10%). All cultivar pectin samples had lower molecular weight (Mw) than CCPp and showed two fractions, indicating the degradation effect of MSE treatment. Monosaccharide analysis demonstrated that LEPp, POPp, ORPp, and GRPp had more branched RG-I regions (40.50–68.48 mol%) than CCPp (30.74 mol%), with high contents of arabinose (Ara) and galactose (Gal). The lower degree of methoxylation of cultivar pectins was verified by FT-IR and NMR. For the macromolecular features, pectins recovered by MSE showed better functional applications than CCPp. Specifically, LEPp and POPp had superior thermal stability, and GRPp showed a higher viscosity and an enhanced emulsifying activity. In addition, the immunochemical study suggested the pectic epitopes masking phenomenon of citrus particle surface, indicating the linkages between xyloglucan, RG-I, and HG polysaccharides, and confirming the contributions of MSE. The results provided novel knowledge to better understand the manosonication in general targets extraction and proposed fundamental references for cultivars-dependent pectin in industrial applications.