*2.10. Statistical Analysis*

All samples were run at least three times, and results are expressed as means ± standard deviations. A *p*-value < 0.05 was considered statistically significant using Student's

*t*-test with 95% confidence. Statistical analyses were determined using GraphPad Prism 8.0.1 (GraphPad Software, San Diego, CA, USA).

#### **3. Results and Discussion**

#### *3.1. Physical Characterization of the Microencapsulated Powder*

Table 1 shows the physicochemical properties and process parameters for the GCPPE and inclusion complex (IC) (GCPPE+HP-*β*-CD+MD). The process yield obtained by spraydrying for IC (GCPPE+HP-*β*-CD+MD) was 83.8 ± 2.6%, which was two-fold higher than for GCPPE alone (38.4 ± 1.2%). Similarly, the total solids increased 2.6-fold for the microencapsulated formulation. The high yield of powdered microparticles can be attributed to the rapid formation of the drying crust, which prevents the powder from adhering to the drying chamber [29]. Our result constitutes an improvement on the yield (64.5 ± 1.5%) reported by Davidov-Pardo et al. [30], who microencapsulated a grape seed extract using MD. The high values obtained in our work are promising for the development of industrial-scale applications.

**Table 1.** Physical characteristics and process parameters for the grape cane phenolic extract (GCPPE) and inclusion complex (GCPPE+HP-β-CD+MD).


Results are expressed as means ± standard deviations, and values with different superscripts letters in a column indicate significant differences at *p* < 0.05.

> The particle size distribution and median particle diameter were smaller in the IC (GCPPE+HP-*β*-CD+MD) than in the GCPPE alone; the particle sizes were 10.9 μm and 17.5 μm, respectively. According to the literature, the diameter of spray-dried particles depends on the properties of the material, the drying conditions, the atomization method used, and the concentration and viscosity of the encapsulated material [31]. The *span* values of the IC (GCPPE+HP-*β*-CD+MD) and GCPPE were very similar, 6.14 and 6.15, respectively, and were higher than those reported for an aqueous grape skin extract microencapsulated with Arabic gum, polydextrose, and partially hydrolyzed guar gum, which ranged from 1.91 to 5.99 [32]. A lower *span* value is a desirable result, as it indicates a more homogeneous particle size distribution [32].

> The bulk density was 0.10 ± 0.01 g/mL and 0.19 ± 0.01 g/mL for the GCPPE and IC (GCPPE+HP-*β*-CD+MD), respectively, being lower than the values reported for encapsulated rosemary essential oil (0.25–0.34 g/mL) [31] or soy milk (0.21–0.22 g/mL) [20]. The slightly higher bulk density of the IC (GCPPE+HP-*β*-CD+MD) vs. the GCPPE indicates an improved powder flow, as a more densely packed powder reflects weaker forces between the particles [20]. Density is an important factor for the packaging, transportation, and marketing of a microencapsulated product. A dry product with high density can be stored in a smaller container compared to a less dense product [31]. The flowability of the samples was also determined by the angle of repose, which was 34.8◦ ± 0.5 for the GCPPE and 36.9◦ ± 1.3 for the IC (GCPPE+HP-*β*-CD+MD), showing no statistical difference between them. A similar value was obtained in a study on the microencapsulation of bioactive products from a *Moringa stenopetala* leaf extract using MD, where the angle of repose was 37.26◦ ± 1.01 [18].

## *3.2. Surface Morphology: SEM Analysis*

SEM can be used to determine the surface morphology of materials and is recognized as an auxiliary method for monitoring the formation of inclusion complexes. The structure and size of the GCPPE and IC (GCPPE+HP-*β*-CD+MD) in the solid state obtained from the spray-drying process were analyzed through microscopy. Microcapsules should preferably have a slightly spherical form and a uniform and smooth cover with minimum fractures and signs of collapse [33]. The SEM micrographs showed that the GCPPE was composed of a mixture of non-spherical particles with irregular surfaces and other larger spherical microparticles (Figure 1A–C). In contrast, the IC (GCPPE+HP-*β*-CD+MD) was spherical, and without visible pores on a smooth surface; microparticles of a variable size but with similar morphology were observed together (Figure 1D–F). These significant morphological changes are probably due to a loss of crystallinity of the guest molecule after its inclusion in the cyclodextrin [34]. The SEM results provided evidence for the formation of the IC (GCPPE+HP-*β*-CD+MD), which was subsequently supported by mass spectrometry and FTIR analysis.

**Figure 1.** Scanning electron microscopy micrographs of the GCPPE (**A**–**C**) and IC (GCPPE+HP-*β*-CD+MD) (**D**–**F**) at different magnifications.
