*3.3. FTIR Analysis of Spray-Dried Powders*

FTIR-ATR is a useful method to detect the formation of inclusion complexes, which are revealed by changes in the FTIR spectra, such as the reduction, disappearance, or shift of absorption bands, due to weak intermolecular interactions [35]. The FTIR spectra of the GCPPE, HP-*β*-CD, IC (GCPPE+HP-*β*-CD+MD), and physical mixture (PM) (GCPPE/HP-*β*-CD/MD) are shown in Figure 2.

**Figure 2.** FTIR-ATR spectra of the GCPPE (**red**), HP-*β-*CD (**purple**), IC (GCPPE+HP-*β*-CD+MD) (**blue**), and PM (GCPPE/HP-*β*-CD/MD) (**green**).

The FTIR spectrum of the GCPPE (Figure 2, red) showed specific bands associated with phenolic compounds (in bold). The peaks at 1602 cm−<sup>1</sup> and 1448 cm−<sup>1</sup> were owing to the C=C stretching vibration of the phenolic aromatic ring and the C–H bending vibrations of the CH2 groups. The peak at 1239 cm−<sup>1</sup> was assigned to C=O stretching of gallic or ellagic acid components due to the presence of hydrolyzable tannins [36]. The band at 1513 cm−<sup>1</sup> was due to the C–C benzene skeletal vibrations of stilbenoids. The strong band at 1032 cm−<sup>1</sup> is attributed to C–O stretching in phenolic compounds [22]. Moreover, the band at 831 cm−<sup>1</sup> was due to the C-H out-of-plane bending vibrations of aromatic compounds. On the other hand, the signals at 2918 cm−<sup>1</sup> and 2850 cm−<sup>1</sup> were related to the CH2 asymmetric and symmetric stretch vibration in aliphatic hydrocarbons [37]. Additionally, a peak at 1103 cm−<sup>1</sup> was observed owing to the C–H in-plane bending vibration [36].

The FTIR spectrum of HP-*β*-CD (Figure 2, purple) showed bands at 3341 cm−<sup>1</sup> due to O–H stretching vibrations and 2927 cm−<sup>1</sup> due to C–H stretching vibrations. The peaks at 1645 cm−<sup>1</sup> correspond to the bending of H–O–H, at 1151 cm−<sup>1</sup> to C–O vibration, and at 1020 cm−<sup>1</sup> to the C–O–C symmetric stretching vibration. The peak at 849 cm−<sup>1</sup> was due to an α-type glycosidic bond [38]. The band at 1080 cm−<sup>1</sup> was ascribed to C–C stretching vibrations, and the peak at 1410 cm−<sup>1</sup> to C–C–H and O–C–H bending [39]. The presence of the hydroxypropyl group was recognized by a peak at 2970 cm−<sup>1</sup> corresponding to the antisymmetric vibration of methyl groups. Additionally, a peak was observed at 1367 cm<sup>−</sup>1, which was ascribed to the bending vibration of the methyl group [40].

The spectrum of the IC (GCPPE+HP-*β*-CD+MD) (Figure 2, blue) shows that some of the characteristic peaks of the GCPPE and HP-*β*-CD have shifted, decreased, or disappeared. The bands at 1645 cm−<sup>1</sup> and 1020 cm−<sup>1</sup> of HP-*β*-CD have shifted to 1634 cm−<sup>1</sup> and 1015 cm−1, respectively, in the IC. Two peaks of the GCPPE at 1239 cm−<sup>1</sup> and 1513 cm−1, ascribed to the presence of hydrolysable tannins and stilbenes, respectively, have shifted to 1246 cm−<sup>1</sup> and 1514 cm<sup>−</sup>1, showing a sharp reduction in intensity due to the complexation, whereas the peak at 2850 cm−<sup>1</sup> disappeared. Furthermore, the bands of the GCPPE at 1602 cm−<sup>1</sup> and 1448 cm<sup>−</sup>1, related to the phenolic aromatic ring, completely disappeared in the IC (GCPPE+HP-*β*-CD+MD). These findings may indicate that the phenolic rings became embedded in the HP-*β*-CD cavities.

The FTIR spectrum of the PM (Figure 2, green) showed a simple overlap between the individual components of GCPPE, HP-*β*-CD, and MD. Insignificant variations in intensity were detected, indicating a mixture of the three components without interactions between them.
