This study used an in vitro human fecal batch fermentation model to show that the proportion of the rhamnogalacturonan-I (RG-I) domain in pectic polysaccharides recovered from citrus canning wastewater significantly influences their fermentation characteristics, with a higher RG-I domain leading to greater short-chain fatty acid production and favorable modulation of the gut microbiota. The main limitation is that the structure-function relationship and potential health benefits require confirmation in in vivo human studies.