## 3 Characterization of Food-Grade Systems
### Technological Characterization
#### 3.1.5 Stability
This was associated with a color transition from green to yellow indicating chlorophyll degradation. These phenomena were absent in the analysis of encapsulated chlorophyll. In fact, the absorption peak at 670 nm decreased only slightly after 56 days and the dispersions showed a constant green color. However, the authors point out the possibility of degradative phenomena as a result of the slow diffusion of water and oxygen through the matrix. To demonstrate the enhanced stability of the crystal-encapsulated compounds, they and the nanoparticles alone were tested at room temperature under strong simulated solar irradiation. Chlorophyll retention was monitored by measuring its fluorescent intensity, since chlorophyll catabolites obtained from the photodegradation process are not fluorescent. After 109 h, encapsulated in the nanoparticles, less than 10% of the chlorophyll remained, as light had greatly accelerated its degradation. In contrast, 80% of the chlorophyll encapsulated in the crystalline composites did not degrade. Therefore, calcite crystals, with a dense and highly ordered structure, could provide an excellent barrier to protect chlorophyll from hostile environments, resulting in increased stability [137]. Other researchers focused on the impact of nanoencapsulation in a xanthan gumb-shellac matrix on the thermal stability of cinnamon extract. The test was conducted in a water bath at a temperature of 90 \({}^{\circ}\)C. Samples were collected after 20 min of heat treatment. The total phenolic content and antioxidant activity (phosphombolybdenum and FRAP methods) of the samples before and after heat treatment were analyzed. After heat treatment, the polyphenol retention of the free cinnamon extract was about 84%, while that of the nano-encapsulated form was 94%. However, nanoencapsulation was not able to perfectly prevent the thermal degradation of cinnamon polyphenols, probably due to a proportion of unencapsulated polyphenols, as confirmed by the encapsulation efficiency of 30%. In fact, the nano-encapsulated cinnamon extract had an antioxidant activity of 88% versus 85% of the free extract [138]. A study published in Food Chemistry addresses the stability of simulated GIT, pH and ion (NaCl) environments of nanoparticles based on a ternary zein/tea polyphenol/pectin complex loaded with HYP (Z/TP/P-HYP). The potential application of Z/TP/P-HYP as a vehicle for oral administration of HYP was studied by evaluating its stability under conditions simulating gastrointestinal conditions. Specifically, the conditions of the fasting stomach (pH 2.0 and presence of pepsing), fed stomach (pH 4.0 in presence of pepsing) and intestine (pH 7.4 in presence of pancreatin) were simulated. After 2 h under gastric conditions at pH 2.0, the Z-HYP nanoparticles aggregated (probably due to the presence of zein) to form particles larger than 300 nm (PDI \(>\) 0.3). They showed increased stability after 2 h of incubation under pH 4.0 conditions. Even after 4 h of incubation under intestinal conditions, Z-HYP exhibited aggregation (probably due to reduced charge). The presence of pectin and TP-pectin (providing a steric stabilizing effect) is the probable cause of the improved resistance of Z/P-HYP and Z/TP/P-HYP to pancreatin digestion. These data allow us to affirm the high application potential in colon-targeting. The ionic stability of the systems was investigated in the pH range of 2.0-8.0. The samples, after dilution, were brought to the desired pH using a 1.0 mol/L hydrochloric acid solution or a 1.0 mol/L sodium hydroxide solution. At pH 6.0, a significant increase in Z-HYP particles was observed with subsequent aggregation probably due to the presence of zein (isoelectric point at pH 6.2). In fact, as pH increased, the zeta potential of Z-HYP changed from positive to negative and then became neutral at pH 6.0. Z/P-HYP and Z/TP/P-HYP showed no significant size and zeta potential changes and better stability against aggregation over the pH range examined.