# Stabilization of Argan Oil Nanoemulsions Using Chitosan Extracted from Pink Shrimp Shells
## 3 Results and Discussion
### Nanoemulsion
#### 3.2.1 Effect of Chitosan on Formulation Thermodynamic and Storage Stability  
The thermodynamic and storage stability of chitosan-stabilized nanoemulsions was evaluated under varying conditions, including rapid temperature fluctuations and storage for six months at ambient temperature, refrigeration, and accelerated aging conditions (Table 2). The nanoemulsions exhibited excellent stability under temperature fluctuations and at 4 \({}^{\circ}\)C, showing no evidence of oil phase separation, creaming, or sedimentation upon visual inspection. At higher temperatures (25 \({}^{\circ}\)C and 40 \({}^{\circ}\)C), the presence of chitosan significantly improved the storage stability of the nanoemulsions, highlighting its strong stabilizing properties. Increasing chitosan concentrations effectively enhanced stability by reinforcing mechanisms that prevent droplet coalescence and aggregation. Higher concentrations of chitosan provided more amino groups that adsorbed onto the surfaces of the nanoemulsion droplets, increasing electrostatic repulsion between them. This created a denser and more robust polymeric barrier around each droplet, contributing to a stronger steric stabilization [16]. The improved stability ensures that the nanoemulsions remain homogeneous and effective over extended storage periods, making them suitable for a range of applications. Compared to conventional stabilizers such as synthetic surfactants (e.g., Tween 80, SDS) and proteins (e.g., casein, whey protein), chitosan exhibits superior stabilizing properties by providing both electrostatic and steric stabilization. Synthetic surfactants primarily reduce interfacial tension but may be less effective in preventing long-term destabilization, while protein-based stabilizers can be sensitive to pH and ionic strength variations, leading to aggregation or phase separation over time. In contrast, the chitosan-stabilized nanoemulsions in this study demonstrated enhanced robustness under various storage conditions, \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Formulation**} & \multirow{2}{*}{**Chitosan (\%)**} & \multicolumn{3}{c}{**Storage Stability (Days)**} \\ \cline{3-5}  & & **4 \({}^{\circ}\)C** & **25 \({}^{\circ}\)C** & **40 \({}^{\circ}\)C** \\ \hline
1 & 0.00 & \textgreater{}180 & 62 & 3 \\ \hline
2 & 0.05 & \textgreater{}180 & 90 & 29 \\ \hline
3 & 0.10 & \textgreater{}180 & 114 & 53 \\ \hline
4 & 0.25 & \textgreater{}180 & \textgreater{}180 & 132 \\ \hline
5 & 0.50 & \textgreater{}180 & \textgreater{}180 & \textgreater{}180 \\ \hline \end{tabular}
\end{table} 
Table 2: Effect of chitosan concentration on formulation storage stability. including elevated temperatures and rapid thermal fluctuations. These results highlight chitosan's potential as a natural, effective alternative to traditional stabilizers for improving nanoemulsion stability. 2.2 Effect of Chitosan on pH Value, Viscosity, Average Droplet Size, Polydispersity Index, and Zeta Potential  
The addition of chitosan and its increasing concentration caused a slight decrease in the nanoemulsion's pH value (Figure 4). This reduction is attributed to the acetic acid used in preparing the chitosan solution, particularly at higher chitosan concentrations. Chitosan also significantly influenced the viscosity of nanoemulsions. Uncoated formulations exhibited typical viscosity levels for nanoemulsions (Figure 4), primarily determined by their oil-to-water ratio, where higher oil content increased viscosity [24]. In contrast, chitosan-decorated nanoemulsions showed markedly higher viscosities. These chitosan-coated formulations showed a progressive increase in viscosity with higher CS concentrations, a phenomenon consistent with previous observations in similar systems [25]. This concentration-dependent viscosity increase has important implications for various applications.