Stability and rheological behaviors of different oil/water emulsions stabilized by natural silk fibroin

• We prepared the oil/water emulsions stabilized by natural silk fibroin.
• Stability and rheological behaviors of the emulsions were investigated.
• Gel-like colloidal networks make emulsions show elastic behaviors.
• Stress overshoot appears due to droplet deformation before association breakage.
• Large modulus, viscosity and yield stress enhance emulsion creaming stability.

In this study, oil/water emulsions stabilized by natural silk fibroin were prepared, and the effects of silk fibroin concentration (φSF), oil volume fraction (ϕo) and oil type on the stability and rheological behavior investigated. After creaming and reaching a stable state, the residual emulsion fraction increases with an increase in φSF, ϕo and oil polarity, while the size of emulsion droplets decreases with an increase in φSF and oil polarity but a decrease in ϕo. Due to the colloidal networks formed by the dispersed oil droplets, the emulsions show a predominantly elastic behavior with a frequency independent modulus and low phase angle. However, the droplet networks are not very strong, and a remarkable shear-thinning behavior occurs for all emulsions during steady shear flow. Moreover, stress overshoot also appears for some emulsions with low φSF and polar oil during transient shear flows, due to the deformation of droplets before the breakage of their associates. The modulus, viscosity and yield stress become larger with the increase of φSF, ϕo and oil polarity, which is very beneficial for strengthening the creaming stability of the emulsions.

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