Inulin at low concentrations significantly improves the gelling properties of oat protein – A molecular mechanism study

• Oat protein formed percolating network via interactions among protein monomers.
• Addition of small amounts of inulin greatly increased oat protein gel strength.
• Phase separation led to inulin nanoparticles in the void spaces of protein network.
• Phase separation and filling effect of inulin explained the improved gel strength.

The effect of inulin addition at low concentrations (0.1–0.5%) on the thermal gelation of oat protein gels was investigated using textural profile analysis, rheological measurements and microstructure observation through scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Results indicate that oat protein hexamers were dissociated with heat into monomers, which then became the reactive units involved in the development of a unique percolating network. The major forces responsible for the establishment of the structure were disulphide bonds, as well as hydrogen bonds and hydrophobic forces. A small amount of inulin can greatly increase the compressive stress of the gels prepared at pH 7 from 13.93 to 22.98 kPa. This is related to the phase separation phenomena produced during heating, which increased the apparent protein concentration. Moreover, inulin formed nanoparticles in the void spaces of the protein network performing a filling effect and creating junction zones. Localized interactions such as hydrogen and hydrophobic bonds were possible between protein and inulin at the borders of junction zones. This research has provided a new approach to make strong oat protein gels at neutral pH. Future applications may promote the utilization of oat protein as a plant derived gelling ingredient in a wide range of food applications.

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