Modelling the non-linear interfacial shear rheology behaviour of chickpea protein-adsorbed complex oil/water layers

The objective of this work is the evaluation of chickpea protein adsorption at oil/water (O/W) interface as a function of protein concentration and pH value (2.5, 5.0 and 7.5). To assess molecular interpretation, interfacial tension is determined as a function of concentration with a Wilhelmy plate, whereas interfacial small amplitude oscillatory shear (i-SAOS) properties are determined using a double wall-ring (DWR) geometry controlled by a DHR3 rheometer (TA Instruments) and a pendant drop tensiometer (IT Concept) is used to determine linear viscoelastic dilatational measurements. This work provides a model which could predict both the linear and nonlinear viscoelastic behavior of complex fluid-fluid interfacial layers. To this end, relaxation tests using the DWR device are carried out at the interface under the linear and non-linear regimes. Steady state viscosity values are also obtained to check the ability of the model to predict the interfacial flow behaviour. Results show that the Wagner-I model can reproduce fairly well the steady state flow behaviour of chickpea protein-adsorbed interfaces. This model is based on the use of a memory function calculated from the generalized Maxwell (obtained from i-SAOS measurements) and a damping function obtained by the Laun model from linear and non-linear relaxation tests.