Impact of pectin characteristics on lipid digestion under simulated gastrointestinal conditions: Comparison of water-soluble pectins extracted from different sources

Four kinds of water-soluble pectin (WSP) extracted from hawthorn (HWSP), apple (AWSP), peach (PWSP), and carrot (CWSP) were mixed with oil-in-water emulsion to investigate pectin characteristics on lipid digestion under simulated gastrointestinal conditions. All WSPs were comprehensively characterized by the degree of methoxylation, neutral sugar composition, molecular weight and conformational parameters, intrinsic viscosity, the degree of linearity and branching, as well as molecular morphology observation by atomic force microscopy. The results demonstrated these WSPs possessed different structural characteristics. The molecules of HWSP were of small size with extended short and linear main chain, forming a certain amount of aggregations in the solution, while the molecules of PWSP were of large size with long and branched chains, forming intensive network structure. The molecular chains of AWSP and CWSP were both of medium size and tended to be flexible random coils in solution forming extensive entangled structures. The apparent viscosity of HWSP and PWSP solutions were both higher than those of AWSP and CWSP due to the aggregations or network structure. And the solution of PWSP showed better anti-shear ability than that of HWSP due to the strong cross-linking between molecule chains. The inhibitory effect of WSPs on lipid digestion decreased with the following order: PWSP, HWSP, CWSP, AWSP, which can be well related with their rheological property. The pectin with large molecular weight and highly branched chains that resulted in strong intermolecular interaction will possess good inhibitory effect on lipid digestion.