## 3 Results and Discussion
### Nanoemulsion Stability During Storage  
Nanoemulsions are colloidal systems that naturally tend to break down by destabilization processes such as sedimentation and creaming. This instability arises due to the presence of droplets with varying sizes and the attractive forces between molecules. While they exhibit enhanced stability during storage, fluctuations in temperature can greatly impact their physicochemical characteristics. Thus, nanoemulsions' kinetic stability was evaluated by monitoring _MDD_ and _PDI_ for 30 d at constant temperatures of 4, 12, and 25 \({}^{\circ}\)C (Table 5). After 30 d, all samples were quite stable in the nanosized range, with a maximum MDD of 345 nm (control at 4 \({}^{\circ}\)C, 2% \(w/w\) oil content). It was observed that, during storage at 4 \({}^{\circ}\)C the MDD values were, on average, higher than MDD during the storage at 12 and 25 \({}^{\circ}\)C. After 30 d of storage, no significant increase in MDD and PDI was observed, but a thin layer of cream was formed on the emulsion surface. The stability of the oil-in-water (o/w) nanoemulsions stabilized by protein from _A. pyrenoidosa_ is largely due to their small initial droplet size and relatively narrow droplet distribution, which help prevent Ostwald ripening for a certain period. These nanoemulsions fall within a kinetically stable regime, where thermodynamics favor droplet growth, but the kinetic energy barrier slows this process. Figure 6 shows the creaming index (CI) of the emulsions with 2% \(w/w\) after 30 d of storage. At 4 \({}^{\circ}\)C the CI of the emulsions was significantly higher than the other storage temperatures, indicating that these emulsions are more stable during storage at temperatures between 12 and 25 \({}^{\circ}\)C. Regarding the oil content, the PDI of samples with 6% \(w/w\) sunflower oil was significantly higher compared to 4% \(w/w\). Additionally, the APPCs from HPH-treated biomass led to nanoemulsions with significantly lower CI compared to untreated biomass, leading to more stable emulsions during storage. The CI of emulsions with 4 and 6% \(w/w\) oil and APPCs from HPH-treated biomass did not show significant differences. These results suggest that the nanoemulsions with 4% \(w/w\) oil content exhibited high kinetic stability, with minimal changes in MDD and PDI values after 30 d of storage. Furthermore, 25 \({}^{\circ}\)C was identified as the optimum storage temperature leading to the lowest CI values. This result is in agreement with [PERSON] et al. (2021), who studied the emulsion stability and emulsification properties of Arabic gum and reported that 22 \({}^{\circ}\)C was the optimum emulsion storage temperature due to the minimization of the creaming index. This result is likely due to the increase in storage temperature approaching the ambient levels, which reduces the surface tension, the emulsion viscosity, and the Laplace pressure (the pressure between the inside and the outside of the oil droplets) across the oil-water interface, ultimately resulting in more stable emulsions [53]. However, non-ionic emulsifiers, such as polysorbates (Tween 20, Tween 80), combined with natural emulsifiers like soy lecithin or sodium caseinate, are effective in stabilizing nanoemulsions, maintaining droplet sizes below 300 nm, and preventing creaming during refrigerated storage for up to two months [4,5,54]. Regarding the HPH biomass treatment, both conditions (600 bar for 1 pass and 800 bar for 4 passes) led to more stable emulsions since their CI values were significantly lower compared to CI of the emulsions with APPC from untreated biomass. Concluding, recovered protein from _A. pyrenoidosa_ can be characterized as effective as commonly used emulsifiers during storage, such as soy lecithin [54], sodium caseinate [55,56], and non-ionic emulsifiers [5,57,58], in maintaining nanoemulsion stability during various temperature storage conditions.