## 3 Results and Discussion
### Influence of Ester Gunn Addition on Ostwald Ripening  
Strongly hydrophobic compounds can be incorporated into the oil phase of essential oil emulsions to inhibit Ostwald ripening [23; 24]. Ester gum is widely used in the beverage industry as a weighting agent [1], but it may play a dual role in stabilizing beverage emulsions by also acting as a ripening inhibitor. The main constituents in ester gum are strongly hydrophobic (Figure 3) [25], which means \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Ester Gunn (\%, \(\upmu\)/\(\upmu\))**} & \multirow{2}{*}{**Viscosity of Oil Phase** (**mPa-s**)} & \multicolumn{4}{c}{**Mean Droplet Diameter (\(\upmu\)m)**} \\ \cline{3-6}  & & **P10 SE** & **P20 SE** & **P23 LE** & **P10 SE** \\ \hline
0.0 & \({}^{\text{E}}\) 1.203 \(\pm\) 0.202 & \({}^{\text{A}}\) 0.557 \(\pm\) 0.031 \({}^{\text{a}}\) & \({}^{\text{A}}\) 0.548 \(\pm\) 0.015 \({}^{\text{a}}\) & \({}^{\text{A}}\) 0.600 \(\pm\) 0.084 \({}^{\text{a}}\) & \({}^{\text{B}}\) 0.599 \(\pm\) 0.042 \({}^{\text{a}}\) \\
2.5 & \({}^{\text{D}}\) 1.368 \(\pm\) 0.021 & \({}^{\text{A}}\) 0.568 \(\pm\) 0.044 \({}^{\text{a}}\) & \({}^{\text{A}}\) 0.603 \(\pm\) 0.027 \({}^{\text{a}}\) & \({}^{\text{B}}\) 0.584 \(\pm\) 0.002 \({}^{\text{a}}\) & \({}^{\text{B}}\) 0.599 \(\pm\) 0.010 \({}^{\text{a}}\) \\
5.0 & \({}^{\text{C}}\) 1.545 \(\pm\) 0.017 & \({}^{\text{A}}\) 0.529 \(\pm\) 0.054 \({}^{\text{a}}\) & \({}^{\text{A}}\) 0.556 \(\pm\) 0.089 \({}^{\text{a}}\) & \({}^{\text{A}}\) 0.647 \(\pm\) 0.066 \({}^{\text{a}}\) & \({}^{\text{A}}\) 0.83 \(\pm\) 0.646 \(\pm\) 0.062 \({}^{\text{a}}\) \\
10.0 & \({}^{\text{B}}\) 1.898 \(\pm\) 0.043 & \({}^{\text{B}}\) 0.431 \(\pm\) 0.030 \({}^{\text{c}}\) & \({}^{\text{A}}\) 0.597 \(\pm\) 0.046 \({}^{\text{b}}\) & \({}^{\text{A}}\) 0.687 \(\pm\) 0.049 \({}^{\text{ab}}\) & \({}^{\text{A}}\) 0.744 \(\pm\) 0.093 \({}^{\text{a}}\) \\
20.0 & \({}^{\text{A}}\) 3.088 \(\pm\) 0.026 & \({}^{\text{B}}\) 0.378 \(\pm\) 0.021 \({}^{\text{c}}\) & \({}^{\text{B}}\) 0.400 \(\pm\) 0.020 \({}^{\text{c}}\) & \({}^{\text{C}}\) 0.490 \(\pm\) 0.007 \({}^{\text{b}}\) & \({}^{\text{B}}\) 0.607 \(\pm\) 0.062 \({}^{\text{a}}\) \\ \hline \hline \end{tabular}  
* The values with different capital letter superscripts in a same column are significantly different by [PERSON]’s multiple range test (\(p<0.05\)). The values with different small letter superscripts in a same row are significantly different by [PERSON]’s multiple range test (\(p<0.05\)).  
\end{table} 
Table 1: Effect of ester gum concentration in the oil phase on the apparent viscosity and the initial droplet diameters (\(d_{43}\), \(\upmu\)m) of orange oil emulsions stabilized using various emulsifiers. Figure 2: Changes in the mean droplet diameter (volume-length mean diameter, \(d_{43}\)) of orange oil-in-water emulsions stabilized with ethylene glycol alkyl ether emulsifiers. that they have a very low water-solubility. For this reason, we examined the impact of ester gum addition on the stability of model beverage emulsions formulated using different kinds of surfactant. As shown in Figure 4, the addition of ester gum to the oil phase prior to homogenization retarded droplet growth in the emulsified orange oil during storage, which suggests that it was effective at inhibiting Ostwald ripening. The presence of the ester gum also impacted the droplet size of the initial emulsions, in a manner that depended on the surfactant type (Table 1). The initial droplet size of the P100 SE-stabilized emulsions did not depend on the ester gum content. Conversely, there was a significant decrease in the initial droplet size of the orange oil emulsions stabilized using P10 SE, P20 SE, and P23 LE at the highest ester gum level used (20% in oil phase). These results suggest that the presence of the ester gum either facilitated droplet disruption in the homogenizer during emulsion formation, or more likely, inhibited droplet growth promoted by Ostwald ripening during and after homogenization.