Role of gelation temperature in rheological behavior and microstructure of high elastic starch-based emulsion-filled gel

Gelation temperature is a critical factor for starch-based emulsion-filled gel structure design. Its role in the rheological properties under small and large amplitude oscillatory shear and microstructure containing interfacial construction and matrix network of emulsion-filled gel with starch as emulsifier and polymeric gel matrix was investigated for the first time. The gel was found to maintain high elasticity over entire gelation temperature range of 55–90 °C, confirmed by frequency sweep, creep-recovery, and Lissajous curves analysis. Intact starch granules and/or starch molecules in emulsion-filled gel systems varied with temperature, which regulated interfacial structure and gel matrix. The interfacial network was visualized by cryo-scanning electron microscopy in this study. Starch molecules were preferentially adsorbed at the interface over granules. And at 55 °C, the starch molecules leached out from granules to form an active-filled emulsion gel network by connecting the granules and/or oil droplets. Increasing temperature to 60 °C enhanced gel strength related to swollen granules filling volume, while strength decreased at higher temperatures by granule disintegration. Differently, the resistance of emulsion-filled gel to large deformation causing structural destruction increased monotonically with temperature, accompanied by a significant increase in their critical strain from 2.01% to 80.32%, suggesting more stretchable structure. This was supported by a strongly interacted emulsion-filled gel system with enhanced oil-starch interfacial interaction and denser molecular matrix network. And structural variations were further correlated to their nonlinear behavior by Higher harmonics, Chebyshev coefficient, and Lissajous curves analysis. This work could provide guidance for starch emulsion gel structure design and/or practical application in food industry.