## 3 Results and Discussions
### Yeast Films Characterization
#### 3.3.9 Digestibility of YFs  
To determine the stability of the protein content and the antioxidant activity with simulated gastrointestinal conditions, the YF samples were incubated under in vitro gastrointestinal conditions. The results presented in Figure 10 showed that the protein contents after 2 h of gastric digestion for the control (2.21 \(\pm\) 0.02 mg/mL) and YF1 (2.26 \(\pm\) 0.04 mg/mL) were approximately equal, while the YF3 (1.98 \(\pm\) 0.14 mg/mL) and YF2 (1.77 \(\pm\) 0.01 mg/mL) samples showed a slight decrease. This suggests that gastrointestinal digestion occurred faster in YF2 and YF3 samples compared to in YF1.  
Regarding the protein content after intestinal digestion, it can be observed that the control (1.7 \(\pm\) 0.05 mg/mL) and YF1 (1.72 \(\pm\) 0.05 mg/mL) samples had the same trend, whereas YF3 (1.9 \(\pm\) 0.01 mg/mL) and YF2 (2.0 \(\pm\) 0.03 mg/mL) samples showed a small increase.  
The results from Figure 11 showed that, in the case of sample YF1, an increase in the antiradical activity after 2 h of gastric digestion (45.3 \(\pm\) 4.8%) due to the presence of essential oil (EO), compared with the control sample (28.18 \(\pm\) 0.19%), which had no EO in the films' composition. Although there were small variations in the composition of YF3 and YF2 samples, we could observe a decrease in their antioxidant activity, 12.97 \(\pm\) 0.6%  
Figure 10: Protein content after 2 h of incubation in a gastric (SGJ) shown in dark grey) and intestinal (SIJ) shown in light grey) environment. Different letters (lowercase letters represent SGJ; uppercase letters represent SJJ) show significant differences (\(p\)-value < 0.05) by [PERSON]’s post hoc test determined by ANOVA (\(p\)-value: 0.005 for SGJ and 0.003 for SIJ).  
Figure 9: Dependence of YF’s mechanical properties om the concentration of glycerol and Tween: (**a**) [PERSON]’s modulus (significant differences among samples by ANOVA and [PERSON]’s post hoc test; \(p\)-value = 0.000); (**b**) tensile strength (significant differences among samples by ANOVA and [PERSON]’s post hoc text; \(p\)-value = 0.000). The red circles indicate YF1, YF2, and YF3; the blue diamond markers indicate YF1c, YF2c, and YF3c. Each experimental value represents average \(\pm\) STDEV.  
and 13.19 \(\pm\) 1.5% respectively. This may be due to the composition of the films, which did not allow the release of polyphenolic compounds even after 2 h of gastric digestion.  
The same trend was observed in the case of intestinal digestion, whereas the YF1 sample had an increase in antiradical activity (2.9 \(\pm\) 1.5%) compared with the control sample (0.73 \(\pm\) 0.43%). These results could suggest a controlled release of the polyphenonic compounds with antioxidant activity from the YF1 film component under the tested conditions at the end of the gastric phase.  
In the case of YF2 and YF3, the release of the antioxidant compounds probably took place in the first 2 h of gastric digestion, justified also by the hydrolyzation of the protein matrix. Therefore, the antioxidant remaining activity in the intestinal phase was not as high as in YF1. However, in the case of YF1, most of its antioxidant activity release took place most likely in the intestinal phase since the protein matrix was mostly unchanged after the gastric phase. However, after 2 h of intestinal digestion, the antioxidant activity of YF1 sharply decreased, indicating a release during this phase.  
Thus, considering the protection during the gastric phase and release during the intestinal phase, the film YF1 consisting of 1.00% glycerol, 1.00% Tween, and 2% EO could represent the best functional film option, with an important antioxidant role in the development of new food packaging.