## 3 Results and Discussion
### Stability over Time  
The EI values of sunflower O/W emulsions with different dosages of CMF as emulsifier were studied to measure their stability over time (Figure 2). All measurements were carried out in duplicate, and the average error between the replicates was always under 5%. The evolution of EI was evaluated for 48 h using O/W ratios of 40/60, 50/50, 60/40, and 70/30. At all O/W ratios studied, the emulsions were formed using only CMF, without the use of any additional surfactant or other stabilizers. Results showed that the emulsion phase formed after CMF addition remained stable after 24 h, maintaining the EI values practically constant with time. In all cases, the emulsion phase decreased less than 3% between the first and the second day. One of the main reasons for the efficiently stabilized O/W emulsions in presence of CMF was the amphiphilic surface nature of the microfibers, which originated from the hydrophobic face and hydrophilic edge of cellulose chains, facilitating CMF assembly in the O/W interface [3; 5; 11; 14; 47; 48]. Furthermore, the CMF formed a densely packed network, which acted as a mechanical steric barrier around the emulsion droplets, preventing their coalescence and stabilizing the emulsion phase over time [31; 49; 50], as shown in Figure 3. Additionally, higher doses of CMF created a more entangled network that increased the EI in all O/W ratios studied. Figure 2: Effect of CMF dose on the emulsification index for sunflower oil-in-water (O/W) emulsions: (a) 40/60, (b) 50/50, (c) 60/40, and (d) 70/30. Figure 4 shows emulsion, water, and oil phase distribution after 48 h. The addition of CMF was required in all O/W to form the emulsion phase. At the lowest O/W ratio studied (40/60), the addition of CMF formed a thick creaming layer with a clear aqueous phase below. Increased addition of CMF reduced the aqueous phase and raised the emulsion phase, as expected, by forming an extended network that stabilized the emulsion. These results are according to the study by [PERSON] et al. [13], which used CMF modified with essential oils with antimicrobial properties. On the other hand, an oil phase appeared on the top of the graduated cylinder during the stabilization of the samples when the O/W ratio increased. This was due to the CMF being incapable of enclosing all the oil drops, producing a decrease in the encapsulation efficiency [2]. However, for an O/W ratio, the increasing addition of CMF significantly decreased the oil phase, indicating that a high amount of oil droplets were stabilized by CMF in the emulsion phase. The highest EI was observed in samples with 0.75 wt% and 1.00 wt% of CMF (C and D samples, respectively). Among the samples with 0.75 wt% CMF (C samples), the maximum EI (79.5%) was achieved with a 50/50 O/W ratio. Meanwhile, for samples with 1.00 wt% CMF (D samples), the maximum EI (88.5%) was achieved with a 60/40 O/W ratio. In the case of 70/30 O/W emulsions, the addition of 1.00 wt% CMF was not enough to stabilize all oil droplets. Therefore, higher amount of CMF would be required to increase the EI value. Figure 5 shows an example of the graduated cylinders after 48 h at several O/W ratios and the same CMF dose (0.75 wt% CMF, Figure 4, samples C). It can be seen that the different phases were clearly separated. Microscope images of the emulsion phase (Figure 5a,b) clearly showed the two phases formed, corresponding to emulsion and water phases, at low O/W ratios. Optical microscope images showed that the oil and water phases were completely separated due to CMF enclosing the sunflower oil drops, avoiding their coalescence. Figure 5c,d show the emulsions with higher O/W ratios. It can be seen that an additional oil phase was formed on the top of the graduated cylinder. Figure 4: Stabilization over time results of different O/W emulsions after 48 h. (CMF dosages: 0: 0 wt%, A: 0.25 wt%, B: 0.50 wt%, C: 0.75 wt%, D: 1.00 wt%). Figure 3: Role of CMF in Pickering emulsions.