The continuous aqueous phase and the smallest oil droplets were separated from the larger oil droplets by centrifuging 2 mL of emulsion at 20,000 g for 42 min in a 2-mL microcentrifuge tube and collecting ~ 0.3 mL of the subnatant from the bottom of the tube as previously reported. The size of the colloidal structures present in this subnatant was measured by dynamic light scattering (DLS) (Zetasizer Nano ZS, Malvern Instruments Ltd., Malvern, Worcestershire, UK). The refractive index (unitless) was 1.47 for the dispersed phase, and the absorbance was 0.01.