Shear rheology of water/glycerol monostearate crystals in canola oil dispersions interfaces

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2013-09, Vol.436, p.215-224
• Main Authors: Carrillo-Navas, H., Fouconnier, B., Vernon-Carter, E.J., Alvarez-Ramírez, J.
• Format: Article
• Language: English
• Subjects: adsorption; Aging; Canola oil; Carbon monoxide; colloids; cooling; crystal structure; Crystals; Diffusion; Dispersions; glycerol; Glycerol monostearate crystals; Glycerols; Interfacial shear rheology; particle size; Reconfiguration; Relaxation time; rheology; Shear; Two-relaxation time model; Water/oil interface
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2013.06.021

•GMS crystal size and concentration affected the rheological response of interfaces.•Hookean spring connected serially to two Kelvin–Voigt elements described rheology.•Fast relaxation time related to reconfiguration of crystals at the interface.•Slow relaxation time related to diffusion and adsorption of crystals at interface. 2.0% or 3.0% wt glycerol monostearate (GMS) was put into canola oil (CO) at 70°C, and the dispersions were cooled down to 30°C (cooling rate of 1.0 or 10.0°C/min), in order to obtain GMS crystals in CO dispersions (CDx,y). Particle size, shape, and crystallinity index of CDx,y was determined. Water/oil interfaces were prepared and the shear rheological response of the adsorbed layers was studied at different ageing times. In all the cases, the interfaces exhibited creep compliance-time dynamics, whose experimental data fitted well a model represented by a Hookean spring in series with two Kevin–Voigt elements, providing two characteristic relaxation times. The fast relaxation time was related to the rearrangement of a rigid disordered layer of crystals adsorbed at the interface taking place at small time scales (about 2s) as a consequence of the applied shear; while the slow relaxation time was related to further GMS crystals adsorption from the interface vicinity, which induced a slower rearrangement and reconfiguration of crystals at the interface in the face of shear disturbances. Model parameters values with respect to ageing time showed that the water/oil interface reached an equilibrium state after about 5–7h for higher GMS concentration.