Journal of Colloid and Interface Science, Vol.583, 404-413, 2021
Viscoelastic characterization of the crosslinking of beta-lactoglobulin on emulsion drops via microcapsule compression and interfacial dilational and shear rheology
Hypothesis: Interfacial rheology provides insight into the mechanical properties of adsorption layers on liquid-liquid interfaces, which mediates the stability of emulsion droplets. The use of capsule compression at the scale of an emulsion droplet to probe the interfacial rheology may open up the possibility of testing the interfacial rheological properties of droplets with complex histories and extremely small volumes found in many applications. Experiments: The time dependent interfacial rheological behavior of beta-lactoglobulin adsorption layers on an oil/water interface in the native and crosslinked state was extracted using small oscillatory indentation with atomic force microscopy (AFM). The results of this novel model and experimental approach were compared to the well-established techniques of interfacial shear rheology (ISR) and dilational pendant drop tensiometry that were performed on analogous interfaces. Findings: The tan delta measured between the ISR and AFM measurements provide similar results in an overlapping frequency range, but the viscoelastic moduli G' and G'' differ by several orders of magnitude. This is most likely the result of the different flow fields and the low deformation of the AFM measurements compared to dilational and shear flow fields. (C) 2020 Elsevier Inc. All rights reserved.