Materials and methods
2.1. Material
The oil phase was degummed and bleached soy oil (Imcopa S/A, Brazil). The aqueous phase was distilled water with 1 wt% of NaCl (Vetec, Brazil). The emulsifiers were soy lecithin (Imcopa S/A, Bra- zil) and Tween 80 (Vetec, Brazil).
2.2. Preparation of emulsions
The emulsions were prepared by the dispersion of 2 or 5 wt% of the emulsifier (soy lecithin or Tween 80) in the oil phase and then addition of the aqueous phase. The ingredients were then mechan- ically stirred (4000 or 9000 rpm) in glass vessel with a volume of 250 mL, using a Silverson L4RT homogenizer (Silverson Machines Ltd, UK), during 3 min at 20 °C. The emulsions were prepared rang- ing from 70 to 90 vol.% of oil phase.
The initial emulsions were O/W and the inverted ones were W/O.
2.3. Emulsion inversion
2.3.1. Conductivity measurements
The emulsion was verified by using a conductivity meter (Shoot Lab 970, SI Analytics GMbH, Germany) to measure the conductivity of the emulsion. High conductivity values indicate that water is the continuous phase and oil is the dispersed phase in a O/W emulsion while for a W/O emulsion, the conductivity values will be low (Thakur et al., 2008).
2.3.2. Stability
The stability of the emulsions were determined by evaluating phase separation of 10 ml samples placed in a conical graduate tubes after 1, 4, and 24h at 10 and 25°C.
2.3.3. Microscopic analysis
A Zeiss Axio Observer D.1 inverted light microscope was used (Zeiss Vision GmbH, Germany) with 1008