## 3 Results and Discussions
### Droplets Size Evolution  
#### 3.2.1 Droplets Formation during Preparation  
To create a stable emulsion, the droplets have to form within the small range sizes, which are achieved by mechanical agitation. Intensity and duration of agitation depend on the time required to homogenize uniformly ingredients. The droplets formation are then produced into two steps: (1) droplet disruption; and (2) droplet coalescence [2]. In this work, droplets disruption was carried out by mixing two phases at which the aqueous phase was introduced drop by drop into the oil phase at the shearing rate of 3000 rpm in 5 min. The rate was then increased step by step up to 14,000 rpm in 5 min. The results of droplets formed during the disruption process are shown in Figure 3. \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**Size**} & \multirow{2}{*}{**T\({}^{\bullet}\)(\({}^{\circ}\)C)**} & \multirow{2}{*}{**T\({}_{\text{m}}\)(\({}^{\circ}\)C)**} \\ \cline{2-2} \cline{4-5}  & **Mass** & & & **Diameter, O** \\ \hline Sample aqueous solution & 30 mg & 1 mm & \(-\)14 & 0 \\ \hline Sample w/o emulsion & 30 mg & & & \\ - dispersed droplet & & 4 μm & \(-\)39 & 0 \\ - oil phase & & - & \(-\)50 & \(-\)33 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Freezing and melting temperature of the samples. Figure 3: Observation droplets formation during droplets disruption by (**a**) DSC test; (**b**) laser diffraction granulometry; and (**c**) optical microscopy. At the lower speed, 3000 rpm, the water and oil phases are disrupted and intermingled. By increasing the shearing speed to 6000 rpm, the droplets started to form. The freezing temperature was found at T* = -15.4 \({}^{\circ}\)C (Figure 3a, solid line), however the exothermic peak is still located around the bulk aqueous phase. The shape of the peak is sharp which implies that a large amount of water has frozen at the same time, so the energy is released in a very short time. In line with the increasing of the shearing rate to 10,000 rpm, the T* moves to the lower temperature -15.8 \({}^{\circ}\)C (Figure 3a, dashed line) with the tail shifted along with the lower temperature. It reflects the droplets not being completely emulsified yet. As the rate attains to 14,000 rpm (Figure 3a, dotted line), the disruption leads the larger droplets to the smaller ones. Two peaks are found in the thermogram, namely T* = -21.3 \({}^{\circ}\)C and T*= -27 \({}^{\circ}\)C, which indicate that the polydispersed population of the droplets with the presence of large droplets dominated the emulsion system. The peak at -51 \({}^{\circ}\)C is the solidification of the oil phase. The volume mean droplet size distribution, D43 decreased step by step from D43 = 488 \(\upmu\)m at 6000 rpm to D43 = 451 \(\upmu\)m at 10,000 rpm then to D43 = 153 \(\upmu\)m at 14,000 rpm. The microscopic observation shows that the distribution of the droplets is in a heterogeneous population, but a small population of large droplets begin to present as the speed increased. The thermograms reveal that in the first 5 min of stirring, T* = \(-23.4\)\({}^{\circ}\)C (Figure 4a, solid line). An asymmetrical signal correlates to the polydispersed population of the droplets. This result corresponds to the microscopic observation at which big droplets displayed in some parts of the image (Figure 4c, 1). The size of the mean droplet is D43 = 102 \(\upmu\)m. For the next 5 min, T* shifts to the lower temperature of \(-33.3\)\({}^{\circ}\)C (Figure 4a, dashed line), the peak is slightly similar to the one in Figure 2, _ii_. The image shows that the big droplets disappeared then spotted in a smaller one to fluctuate randomly in size (Figure 4c, 2). The mean size of these droplets is 15 \(\upmu\)m. After 15 min, T* is found \(-35.6\)\({}^{\circ}\)C (Figure 4a, dotted line), the peak is a bell shape that implies emulsion with the monodisperse distribution. This is in favor of the optimum time for the coalescence of the droplets. This result is in agreement with optical microscopy.