abstract
- Phenolic compounds from fruit agro-industrial by-products are valuable bioactives but exhibit limited stability and bioaccessibility during digestion. This study evaluated calcium-induced alginate ionic gelation for encapsulating phenolic-rich extracts from ultraviolet A (UVA)-biofortified strawberry and apple by-products. Microcapsules were characterized for encapsulation efficiency, morphology, and in vitro gastrointestinal stability and bioaccessibility. Encapsulation efficiencies reached 73% for strawberry by-product and 87% for apple peel extracts. Scanning electron microscopy revealed compact, irregular microspheres (700¿800 µm) with limited surface porosity. In vitro digestion showed that alginate microcapsules restricted phenolic release during salivary and gastric phases while enhancing intestinal release. Encapsulation significantly increased intestinal bioaccessibility, reaching 38.7% for strawberry and 53.8% for apple microcapsules. The combined application of UVA light, ultrasound-assisted extraction, and alginate encapsulation increased phenolic bioaccessibility by up to 153% for strawberry by-products and 112% for apple peel extracts. These results demonstrate that alginate ionic gelation effectively modulates phenolic stability and release, supporting the chemical valorization of fruit by-products, and potential incorporation into functional food systems.