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

• 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 2 s) 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 5–7 h for higher GMS concentration.

Figure optionsDownload as PowerPoint slide