Alginate Edible Films as Delivery Systems for Green Tea Polyphenols

This study investigated the potential of alginate edible films to act as vehicles for the delivery of polyphenols to the intestinal tract. Sodium alginate (0.5–2% w/v) and green tea extract (GTE, 25–50% w/w) were combined to form films with different microstructural properties via the casting method, where their physical, mechanical and barrier properties were analysed. Release studies into a 50% ethanol (v/v) food simulant and under simulated in vitro digestion were also conducted, and the resulting kinetics of polyphenols release was investigated. Composite alginate films with 25% w/w GTE (E∼2500 MPa; EAB∼14%; k∼0.04) showed significantly enhanced mechanical properties and slower rates of polyphenol release than samples with 50% w/w GTE (E∼6000 MPa; EAB∼6%; k∼0.18). Polyphenols entrapped within the 2% alginate – GTE films were successfully released during digestion (∼54%), demonstrating their bioaccessibility and availability for absorption by the gastrointestinal tract. The bioaccessibility of green tea polyphenols was significantly enhanced by films with good sustained-release effect (2% alginate – GTE, C/C0 = 54.41±0.75%) respect to the free GTE (C/C0 = 33.73±6.57%). These findings highlight the versatility of bioactive alginate edible films and create a blueprint for the design of sustainable active packaging alternatives with dual functionality.