Structural responses of zein-based oil-in-glycerol emulsion gels during freeze-thawing and heating

The current study developed zein based oil-in-glycerol emulsion gels, and tested the roles of different structural components (oil droplets, interface, and network structures) on the properties of the gels when subjected to freeze-thawing and heating. Different structures of the systems were obtained by changing the content of zein, oil, and Span 20. Docking results showed the hydrogen bond, hydrophobic interactions and hydrogen bond, hydrophobic interactions were key interactions between zein-glycerol, zein-oil, zein-Span 20, respectively. Freeze-thawing stability of emulsion gels got declined with the increase in the content of zein, oil and Span 20, and the content of zein played a more significant role. The oil holding capacity and solvent binding capacity of gels were decreased with more cycles of freeze-thawing. Heating process reduced the solvent holding capacity of gels, which was due to the weakened hydrogen bonding of zein-glycerol, and enhanced zein-zein interaction. Gel strength of the systems was significantly enhanced after heating, indicating the denaturation and rearrangement of zein structures in the continuous phase. Overall, the interface and continuous network of zein played crucial roles in tuning the stability of emulsion gels against thermal changes. This study provided novel information regarding the structure-relationship in zein based emulsion gels, and would be helpful to widen the applications of zein in food products.