## 3 Results
### Bioavailability after Simulated In Vitro Digestion  
To better understand the relationships between the types of extracts and carrier mixtures used, the microcapsules were subjected to simulated in vitro digestion, and the bioavailability index of phenolic compounds was assessed. The obtained results are summarized in Tables 6 and S1. In general, bioavailability defines the amount of an active ingredient released in the gastrointestinal tract from the product matrix that can be absorbed or is bioavailable [40]. The total content of phenolic compounds after digestion ranged from 0.12 (A) to 0.52 (D) mg/g for microcapsules with a CE core and from 3.94 (E) to 21.17 (H) mg/g for microcapsules with a PE core. For all matrices, lower values of phenolic compounds were noted compared to the sample before digestion. The profile of individual compounds was presented in the same way. The bioavailability index of all phenols calculated on this basis ranged from 150.74 (A) to 485.75% (C) and from 289.15 (E) to 845.43% (C), respectively, for microcapsules with CE and PE cores. In both cases, significantly higher bioavailability of phenolic compounds was characteristic for microcapsules obtained from the Alg + WPI mixture, while the lowest was characteristic for microcapsules with Alg. Analyzing the types of extracts, a significantly higher bioavailability index of phenolic compounds was noted for microcapsules with a PE core. Considering the composition of microcapsules for which the highest bioavailability was demonstrated, i.e., those obtained from the Alg + WPI mixture -- with a PE core -- had twice the total bioavailability of phenolic compounds than with a CE core. Nevertheless, it is worth noting that statistically significant differences (\(p<0.05\)) are visible mainly in the bioavailability of other phenolic compounds, i.e., phenolic acids and flavonoids, while the bioavailability of anthocyanins is maintained at a comparable level for both extracts. For microcapsules with a CE core from the group of other phenols, bioavailability was demonstrated only for quercetin 3-O-galactosidase (0.72-95.70%). According to the authors [41], flavonoids, mainly quercetin derivatives, undergo autoxidation and degradation in an alkaline environment, which may explain their lack of bioavailability from the microcapsule matrix. Interestingly, anthocyanins were characterized by generally high bioavailability. The highest values were shown for malvidin 3-O-glucose (104.58%, B) and ponoidin 3-O-galactoside (102.03%, D). According to the literature, this group of compounds is particularly sensitive to enzyme activity and pH of digestive fluids [8], which makes their very low bioavailability a great challenge. Generally, an increase in bioavailability is observed for them in the gastric phase, which can be attributed to low pH, stabilizing anthocyanins and increasing their solubility. However, [PERSON] et al. [42] showed anthocyanin bioavailability of 31.0-123.2% for microencapsulated grape pomace Alg. Analyzing the oral, gastric, and intestinal bioavailability simultaneously, the authors demonstrated high stability in the gastric phase and the highest release in the intestinal phase, i.e., the most desirable release profile. Moreover, for microcapsules obtained via spray drying, a better anthocyanin bioavailability was observed, which was explained by the effect of the carriers [43]. These observations may indicate that the polymer mixtures used allowed for the protection of anthocyanins under simulated in vitro digestion conditions. Thus, encapsulation had a positive effect on the stability of phenolic compounds during digestion, which may indicate the effectiveness of this method in preserving their bioactive properties. It is also worth noting that the chlorogenic acid bioavailability index was recorded only for microcapsules with a PE core, where the highest value (55.51%) was found for the Alg + Pect + WPI (H) mixture.