2.3. Evaluation of kinetic stabilit

2.3. Evaluation of kinetic stability

The phase separation of the emulsions was observed in a 25 mL cylindrical tube (internal diameter = 17 mm), sealed with a plastic cap and stored for 14 days at 25 °C. The oil phase separation was expressed in sedimentation index (SI), which is calculated as the relation between the upper oil phase height (H) and the initial height (H0), as described by Eq. (1):


equation(1)

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In the case of emulsions in which the aqueous phase separated from the emulsion, the percentage of aqueous phase volume in relation to the total volume was calculated.

2.4. Optical microscopy

The emulsion microstructure was observed through an optical microscope (Axio Scope.A1, Carl Zeiss, Germany) at 100× magnification for qualitative evaluation. The images were captured with the software AxioVision Rel. 4.8 (Carl Zeiss, Germany).

2.5. Particle size distribution

The particle size distribution was determined by the laser diffraction method using a Mastersizer 2000 (Malvern Instruments Ltd., UK). The emulsions were dispersed in their respective continuous phase oil: soybean oil and hexadecane (refractive indexes 1.467 and 1.435, respectively). In order to avoid the presence of bubbles, ultrasound was applied for 5 min in the dispersion medium. The measurements were done at laser obscuration between 5 and 15% and at 1750 rpm agitation speed. The particle size distribution was presented in volume fraction, considering the parameters of water droplets (refractive index = 1.33 and absorption = 0.01).