Controlled-release of tea polyphenol from gelatin films incorporated with different ratios of free/nanoencapsulated tea polyphenols into fatty food simulants

Chitosan nanoparticles with different encapsulation efficiencies were incorporated to obtain gelatin films with controlled-release properties. Nanoparticles tended to aggregate as encapsulation efficiency increased, due to the increase in surface tension of film-forming solutions. The addition of nanoparticles increased the compactness and isotherm hysteresis of films, whereas decreased the moisture diffusion. Tea polyphenol released faster and greater from films in 50% ethanol (4 °C) than in 95% ethanol (25 °C) fatty food stimulant due to the swelling by water. However, controlled-release showed in both simulants, where free tea polyphenol had the largest release followed by 51.3%, 83.3% and 96.9% encapsulation efficiency. The diffusion coefficient in 50% ethanol was 2 orders of magnitude higher than that 95% ethanol (10−13 and 10−11 cm2/s, respectively). Films maintained their structures in 95% ethanol after 240 h but not in 50% ethanol. These results might open up new designs in long-term protection for fatty foods.