Structure and rheological properties of extruded whey protein isolate: Impact of inulin

Impacts of inulin addition (0, 5, 10, 15 %) on structure, functional and rheological properties of whey protein isolate (WPI) after extrusion pretreatment (E-WPI) were investigated. The results proved that after adding 15 % inulin, water holding capacity of gels, emulsifying activity, emulsion stability, foaming ability and foaming stability of E-WPI were the best and increased by 24.38 %, 7.43 %, 12.35 %, 162.97 % and 41.31 %, compared with those of unextruded WPI, respectively. Rheology analysis showed that apparent viscosity and consistency index of all the samples after inulin addition were enhanced and exhibited pseudoplastic fluids. FTIR spectroscopy indicated that E-WPI/WPI and inulin was linked together due to hydrogen bonds and addition of inulin increased the proportion of their β-turn structure. These findings demonstrated that the addition of inulin in combination with extrusion pretreatment could jointly improve the functional properties of WPI. Therefore, E-WPI with the addition of inulin shows potential commercial applications in the production of novel food foaming agents and emulsifiers.