Functional characteristics of water-soluble polysaccharides from soybean residue: Pulsed electric field-assisted...

The high-voltage pulsed electric field (PEF) technology was used to extract soluble soybean polysaccharides (SSPS) from soybean residue. A comparison was made between hot water extraction (HWE) method and pulsed electric field-assisted extraction (PAE) method in this study. HWE-P was extracted in hot water at 80 °C for 2 h, while PAE-P was done under the same conditions after soybean residue was treated at 5 kV/cm for 60 pulses. PAE-P yield was 4.80% higher than HWE-P, increasing to 14.33%. Both HWE-P and PAE-P contained glucose, galactose, arabinose, fructose, galacturonic acid, and glucuronic acid. PAE-P exhibited higher uronic acid content and lower molecular weight with a more concentrated molecular weight distribution. FTIR spectra of the two SSPSs displayed characteristic absorption bands of polysaccharides in the range of 4000-400 cm^-1. UV scanning spectra showed that they had no protein residues. Congo red experiments indicated that neither SSPSs possessed a typical triple-helix structure. SEM analysis revealed morphological differences between the two soybean residues and between the two polysaccharides. PAE-P exhibited superior thermal stability by TGA analysis. Steady-state shear results showed that both PAE-P and HWE-P behaved as non-Newtonian (pseudoplastic) fluids, while dynamic viscoelastic ones suggested that PAE-P solution might had lower gel elasticity. In terms of biological activity, PAE-P demonstrated stronger antioxidant capacity with significantly enhanced scavenging rates of DPPH (2,2-diphenyl-1-picrylhydrazyl) and ·OH (hydroxyl radical), and excellent hypolipidemic activity in vitro, particularly showing stronger inhibitory ability against pancreatic lipase and a higher binding constant with the enzyme.