# Rosehip Seed Oil-Incorporated Chitosan Films for Potential Fruit Packaging Applications
## 3 Results and Discussion  
### Chitosan/RSO Film Morphology  
The morphology of the samples was investigated using scanning electron microscopy (SEM). SEM examination reveals the morphology of the film's surface and bulk (via cross-section) obtained by the incorporation of rosehip oil into chitosan films (Figure 2). The obtained microstructures were qualitatively analyzed, aiming to describe the role of rosehip oil and the homogenization procedure in the structure of the chitosan matrix. As illustrated in Figure 2, the pure chitosan film (Figure 2a) presented a compact and homogeneous structure. However, when RSO is introduced to the chitosan film, particularly at higher concentrations, the microstructure becomes heterogeneous. The presence of RSO caused a heterogeneous structure in which oil droplets were entrapped in the continuous carbohydrate network. The number and size of the lipid droplets were increased with the RSO concentration. Spherical pores with variable dimensions, attributed to rosehip oil droplets distributed randomly within the matrix, can be observed, which could reduce hydrophobic aspects and increase flexibility, providing the film with a more amorphous structure [28; 43]. The presence of these pores is likely due to the flocculation and coalescence of small drops of emulsified essential oil during the drying of the film. The observed structural differences could be explained by the differences in essential oil concentration in the films during drying and caused by the intricate interactions between lipids, polysaccharides, and the solvent [44]. Such behavior likely arises from the deformation forces exerted during the polymer chain aggregation, induced by solvent evaporation [45]. The droplet sizes were calculated, and the results are listed in Table 2. The table presents averaged values with standard deviations for each value. As it can be seen, the droplet size increases at bigger concentrations of the RSO. Similar surface microstructures, namely discontinuities associated with the formation of two phases, was found for a quinoa protein-chitosan-sunflower oil film by [PERSON] et al. [46]. test for the elongation properties and a puncture test for the perpendicular deformation tolerance--see Table 3.  
The tensile strength of pure chitosan film was (62.27 \(\pm\) 6.75) MPa. The addition of the RSO emulsion up to 3% decreased the tensile stress by about three times--(19-20) MPa. The further increase in oil concentration up to 4-5% caused its bigger decrease down to (11.93 \(\pm\) 1.33) MPa. A similar trend can be observed in the values of the tensile modulus, which reduced by almost half--from (1.016 \(\pm\) 0.547) GPa to (0.544 \(\pm\) 0.725) GPa when 3% oil emulsion was added. Above this emulsion concentration, the tensile modulus dropped to (0.470 \(\pm\) 0.852) GPa. The presence of oil in the chitosan films causes a change in their elasticity (deformability), which is expressed as an increase in the strain at break. The pure chitosan film is brittle, with strain at break less than 3%. It rises up to 11% when RSO emulsion with a concentration in the range of 1-3% is added and remains constant (11-12%) when increasing the emulsion concentration up to 5%. These values are comparable with the result of [PERSON] et al. [19], who studied chitosan-based bion nanocomposite films with rosehip oil and montmorillonite nanoclay. The tensile energy of chitosan film was (4.22 \(\pm\) 0.62) N\(\cdot\)mm. The inclusion of RSO emulsion up to 3% resulted in a three to four times increase up to (12.85 \(\pm\) 2.68) N\(\cdot\)mm, (16.00 \(\pm\) 2.57) N\(\cdot\)mm, and (18.82 \(\pm\) 3.19) N\(\cdot\)mm, respectively. At higher emulsion concentrations, it rose 6-8 times, up to (27.43 \(\pm\) 0.30) N\(\cdot\)mm. Similar trends can be observed in the puncture properties of the films. The puncture force decreased from (20.53 \(\pm\) 1.17) N for the pure chitosan film to (13.02 \(\pm\) 1.67) N for the film containing 5% RSO emulsion.