High internal phase emulsions stabilized by pulse proteins and their complexes with pectin: relating 2D interfacial rheology to 3D bulk rheology

High internal phase emulsions (HIPEs) are emulsions with an oil volume fraction above the maximum packing limit. Interfacial rheological properties affect the bulk shear properties of HIPEs, as the deformation of closely-packed oil droplets causes deformation of interfaces of the oil droplets. Which interfacial properties dominate the bulk shear response will depend on the applied shear strain. The interfacial shear and dilatational rheology of lupin and hemp proteins, and lupin or hemp protein-pectin complex stabilized oil-water interfaces were studied in both the linear viscoelastic (LVE) and non-linear viscoelastic regimes (NLVE). The rheological properties of HIPEs were characterized by both steady shear rate tests (0.03-100 s -1 ) and dynamic rheological tests (shear strain sweeps, with strains 0.01-1000%). In the LVE regime, a positive correlation between both the interfacial shear modulus (G i ’) and dilatational elastic modulus (E d ’), and the bulk shear elastic modulus (G’) of HIPEs was found. At strains in the NLVE regime (30% strain), only E d ’ was positively correlated with G’, while G i ’ only had a marginal effect on G’. This is the result of the strong strain dependence of G i ’. Finally, we developed a model to relate E d ’ and G i ’ of oil-water interfaces to G’ of HIPEs, based on the interfacial momentum balance which can explain this dependence of G’ on both interfacial parameters. Our work provides a more fundamental understanding on how surface rheological properties affect the rheology of HIPEs. • Bulk elasticity of HIPEs was positively correlated to interfacial elasticity. • In the LVE regime, both E d ’ and G i ’ affected the G’ of HIPEs. • In the NLVE regime, only E d ’ determined the G’ of HIPEs. • G’ was related to E d ’ and G i ’ by a model based on the interfacial momentum balance.