## 3 Characterization of Food-Grade Systems
### Technological Characterization
#### 3.1.3 Encapsulation Yield and Solid-State Characterization
This confirmed the absence of degradation or alteration processes during formulation and the successful encapsulation of QUE. In addition, the absence of significant changes in the OH stretching band region (3200-3600 cm\({}^{-1}\)) and the C=O stretching band region (approximately 1735 cm\({}^{-1}\)) confirmed the absence of chemical interactions between the flavonoid's carbonyl and carboxyl groups and the polymer. A similar behaviour was observed for the system consisting of EUGC alone, with a %EE of 69%. The encapsulation process was also confirmed by DSC analysis. In fact, the thermogram of microparticles loaded and produced with increasing weight ratios of QUE:EUGB showed no thermal transitions corresponding to QUE. The endothermic peaks recorded around 120 \({}^{\circ}\)C were attributed to dehydration phenomena observed for both pure crystalline QUE and EUGB. XDR analysis also confirmed the homogeneous dispersion of polyphenol within the matrix. Furthermore, these results indicated that the encapsulated QUE was present in a disordered non-crystalline or highly microcrystalline state within the polymer network [41]. Previously, other authors have designed a NP delivery system for the encapsulation of bioactive compounds using QUE as a model. A combination of almond gum (AG) and shellac was used to prepare the system using the antisolvent method. The %EE of the NP made by the biopolymers combination without surfactant was about 78%, and no considerable improvement was observed when the concentration of QUE was increased to 0.05%. In the presence of surfactants (PS 80 or QS) and 0.01% QUE, it was 91 and 87%, respectively, which increased considerably to 99% with 0.05% QUE. The increase in %EE with the addition of a surfactant may be related to the increased solubilization of QUE molecules due to the presence of surfactant and the formation of smaller particles leading to increased saturation solubility. The thermogram of the charged NPs (Figure 13a) showed no endothermic peak at 320 \({}^{\circ}\)C (melting peak characteristic of pure, crystalline QUE) indicating that the drug was well mixed with shellac as a base material within the system and most likely QUE existed in an amorphous form as a solid solution, rather than in crystalline form. It must be emphasized that the amorphization of QUE would enhance its solubility at the gut pH conditions, and thus bioavailability. The FT-IR spectrum (Figure 13b) of charged NPs showed the characteristic peaks of the alcohol group of AG around 1000 cm\({}^{-1}\) and the C-H group of shellac (2860-2930 cm\({}^{-1}\)). In this spectrum, the peak intensity of pure QUE around 1500 cm\({}^{-1}\) (aromatic ring) was clearly reduced indicating that an interaction between QUE and shellac molecules had most likely occurred [111]. A study published in Food Biophysics focused on the development of a zein-sodium caseinate-xanthan gum (Z-SC-XG) nanocomplex for piperine (PIP) delivery. FT-IR spectra of the developed nanocomplex showed a broadening of the peak at 3408 cm\({}^{-1}\) attributable to the hydrophilic O-H stretching of Z and a decrease in the intensity of the hydrophobic C-H stretching at 2924 cm\({}^{-1}\) attributed to CS. These changes are due to the hydrophilic increase in the PIP/Z-SC-XG complex with respect to Z due to hydrophilic XG. In addition, the shift and decrease in intensity of the peaks associated with the amide bonds (amide I, II and III) of SC was detected. Similarly, a decrease in the intensity of the peak associated with the vibration of the carboxyl group of XG was observed. These changes could indicate an interaction between the amine groups of Z and SC and the carboxyl groups of XG as a whole. In addition, in PXDR analysis of PIP/Z-SC-XG, the characteristic peaks of Pip in the solid state were not detected, indicating that it was well encapsulated in the protein and polysaccharide matrix. Additionally, small peaks were detected at 9.6\({}^{\circ}\) and 19.8\({}^{\circ}\) assigned to the presence of zein in the nanocomplex structure.