Physicochemical and Structural Properties of Pomelo Peel Pectin From Majiayou Pomelo With Different Storage Periods

Majiayou pomelo peel (MPP) pectin obtained from Majiayou pomelo with different storage periods (0–150 days) was compared based on physicochemical, structural, functional properties and their correlations. The yield, degree of esterification (DE), molecular weight (Mw), particle size, galacturonic acid (GalA), thermal stability, antioxidant activity (AOA), apparent viscosity, and viscoelasticity of MPP gradually decreased with the extension of pomelo storage periods, possibly due to the fracture of the main chain in the pectin molecule. The DE value of MPP gradually decreased to the range of low-methoxyl pectin (LMP, < 50%) after 150 days of storage probably because of the loss of the –CH₃ group in the main chain of MPP. The color difference, absolute zeta potential, and metal adsorption capacity of pectin significantly increased with the extension of pomelo storage periods (p < 0.05), attributing to the de-esterification of pectin and decrease of GalA via endo-polygalacturonase (endo-PG) activity. Correlation analysis confirmed that high DE, GalA, and low branched Rhamnogalacturonan-I (RG-I) region in pectin could benefit from increasing its antioxidant, thermal stability, and rheological properties. These results suggested that the fresh MPP₀ showed better physicochemical and functional properties for application in pharmaceuticals and cosmetics, and no-freshness MPP (MPP₆₀ and MPP₁₅₀) has good prospects for implementation in foods.