total volume of alginate-oil emulsion. The emulsion was left standing
for 1 h to determine the extent of phase separation, if any. A
duration of 1 h was used because the encapsulation process was
complete within the time-frame. The alginate concentrations used
ranged from 5 to 45 g/L. Higher alginate concentrations were not
attempted because they were difficult to process due to their high
viscosities. The effect of alginate concentration on the ES is shown
in Fig. 3a. The ES was found to increase with higher alginate concentration
(from 40% for the 5 g/L alginate solution to 82% for the 15 g/L
solution). The emulsion was found to be stable, and no phase separation
was observed when the alginate concentration was 25 g/L
and higher. The effect of oil loading on the ES is shown in Fig. 3b.
The emulsion was found to be stable for an oil loading up to 40 vol%.
Further increasing the oil loading (i.e., >40 vol%) resulted in a sharp
decrease in the ES, where 50 vol% of the oil separated out from the
initial emulsion at oil loading of 60 vol%.
The alginate-oil emulsions, prepared from different alginate
concentrations and oil loadings, were observed under a microscope
to estimate the oil droplet size, and the microscopic images of the
oil droplets are shown in Fig. 4. It was found that the oil droplet size
decreased as alginate concentration increased (refer Fig. 4a). Based
on visual estimation, oil droplet size decreased from 100–400 m
to 10–50 m when the alginate solution increased from 5 g/L to
45 g/L. On the other hand, higher oil loading as expected increased
the number density of oil droplet within the emulsion (Fig. 4b). For