Modulation in physicochemical properties and digestibility of potato starch by ethanol-fractionated polysaccharides from Phlebopus portentosus.

In this study, the effects of Phlebopus portentosus polysaccharides on the physicochemical properties and digestibility of potato starch (PS) were systematically evaluated. Alkali-extracted polysaccharides from Phlebopus portentosus (APBP) were fractionated into three subfractions (APBP-30, APBP-70, and APBP-80) through gradient ethanol precipitation. These subfractions differed in monosaccharide composition and molecular weight. Further, PS-APBP subfraction composites were prepared and investigated for their physicochemical and structural properties, as well as in vitro digestibility. Pasting, rheological, and differential scanning calorimetry analyses showed that APBP subfractions led to reduced viscosity and gel strength while increasing the enthalpy of PS. Furthermore, X-ray diffraction analysis revealed an increase in the relative crystallinity of PS from 12.69% to 13.43% and 14.04% after the addition of APBP-70 and APBP-80, respectively. Microscopic structural analysis indicated that the interaction with APBP subfractions promoted the formation of a more compact layered structure and regular microstructure in PS. Additionally, APBP subfractions inhibited the digestibility of PS. Specifically, APBP-30 significantly reduced the rapidly digestible starch content in PS (from 55.77% to 41.08%) by forming a dense, stable protective layer around starch granules. Conversely, APBP-80 exhibited the highest inhibitory effect on enzymatic hydrolysis by increasing crystallinity. It increased the resistant starch content of PS from 8.61% to 23.85%. These findings provide a theoretical basis for improving the processing performance and digestive properties of starch-based food products.