Regulation of nano-encapsulated tea polyphenol release from gelatin films with different Bloom values

Active packaging is an emerging technology for food preservation in recent years, to effectively control the sustained release of antioxidants. Herein, antioxidant films were prepared by using gelatins (100, 150, 225 Bloom values) as film matrix and embedding tea polyphenol (TP)-loaded chitosan nanoparticles (CSNs). Gelatin with high Bloom value had more triple helix structures and more significant entanglements between molecular chains, resulting in more viscous film-forming solutions, which led to a more stable system with better dispersed CSNs. TP and CSNs remained chemically stable and formed new hydrogen bonds with gelatin molecules, but did not significantly affect the secondary structure of gelatin. There was a combined effect between the CSNs dispersion and the gelatin structure on film swelling in fatty food simulants, where the films prepared with the gelatin with lower Bloom value had lower swelling degree. This swelling degree was closely related to the release of TP, since the film prepared with the gelatin with Bloom 100 showed the lowest total release of TP in 50% and 95% ethanol simulants. Also, as expected, the antioxidant activity revealed that the CSNs could effectively control the release of TP from films by inhibiting the migration of TP.