2.2.1. Textural properties

Specific surface areas were measured using N2 adsorption–desorption analysis. Furthermore, bulk and skeletal densities were determined, and porosity was calculated. All values are shown in Table 1.

**Table 1.** Specific surface areas, densities and porosities of pectin aerogels and chitosan-coated pectin aerogels.


Specific surface area of chitosan-coated pectin aerogels is 276 m<sup>2</sup>/g, which is significantly lower compared to pure pectin aerogels, which have a surface area of 441 m<sup>2</sup>/g. It seems that the coating procedure affected the structure of pure pectin aerogels, resulting in smaller specific surface areas. However, the specific surface area of 276 m<sup>2</sup>/g is still high enough for loading of the active substances (such as curcumin) and the potential as a drug carrier. Very high porosities of 96 ± 0.05% and 94.8 ± 0.03% undoubtedly shows aerogels nature of both pectin and chitosan-coated pectin materials.

The N2 adsorption–desorption isotherms for both pectin aerogels and chitosan-coated pectin aerogels, presented in Figure 3 could be classified as type IV isotherms. From the types of isotherms, it can be concluded that the prepared aerogels are mesoporous materials.

**Figure 3.** Adsorption–desorption isotherms for pectin aerogel and chitosan-coated pectin aerogels.

### 2.2.2. Scanning Electron Microscopy

Scanning electron microscopy (SEM) was employed for determining the surface morphology of prepared aerogels. The coating of pectin core with chitosan layer was confirmed by SEM image on a 100 μm scale. Figure 4a undoubtedly shows a two-layer aerogel. The upper layer represents a chitosan coating over a pectin core. Porous structure is visible in both layers. Furthermore, Figure 4b represents the outer part of the coating on a 1 μm scale, confirming the porous structure of the chitosan.

**Figure 4.** Scanning electron microscopy (SEM) images: (**a**) chitosan-coated pectin aerogels, the inner part (100 μm scale); (**b**) chitosan-coated pectin aerogels, the outer part (1 μm scale); (**c**) pectin aerogel (500 nm scale); and (**d**) chitosan-coated pectin aerogels (500 nm scale).

Figure 4c,d present the pore network of pectin aerogels and chitosan-coated pectin aerogels on a 500 nm scale. In both cases, the structure is highly porous, having a complex interconnected network of pores. The structure of pectin aerogels seems to be more compact compared to the structure of chitosan-coated pectin aerogels, which is expected since the specific surface area and porosity of pure pectin aerogels is higher.
