The physicochemical properties of low molecular weight 'Chachi' (Citrus reticulata 'Chachi') pectins prepared by different modification methods and their modulation effects on the human gut microbiota

To explore the prebiotic potential of 'Chachi' pectin (CP), low-molecular-weight 'Chachi' pectins (LCPs) were prepared using pectinase (PP1, PP3) and Fenton (FP2, FP4) methods. Compared to CP, LCPs were enriched in rhamnogalacturonan I (RG-I) structures, exhibited lower degree of methylation, and had significantly reduced particle size and viscosity. Enzymatic hydrolysis was milder, targeting homogalacturonan (HG) regions and yielding LCPs with narrower molecular weight distribution. Fenton reaction was more intense, breaking both HG and RG-I Ara side chains, producing LCPs with broader molecular weight distribution. In vitro fermentation revealed that enzymatically modified LCPs, especially PP3, significantly enhanced total short-chain fatty acids (SCFAs) production by promoting the growth of beneficial bacteria like Bacteroides and Prevotella while inhibiting pathogens such as Klebsiella and Streptococcus. All LCPs demonstrated varying prebiotic effects, with PP3 notably influencing gut microbiota composition. These findings highlight its promise in developing prebiotics targeting gut microbiota regulation. This research provides a foundation for utilizing 'Chachi' peel-derived LCPs as functional dietary fibers.