Preparation of Type-A Gelatin/Poly-γ-Glutamic Acid Nanoparticles for Enhancing the Stability and Bioavailability of (-)-Epigallocatechin Gallate

(-)-Epigallocatechin gallate (EGCG) has gained considerable attention owing to its beneficial properties. However, its application as a functional food is restricted due to its instability and low bioavailability. In the present study, a food-derived nanoparticle system based on type A gelatin/γ-PGA was developed to preserve and deliver EGCG. The EGCG/gelatin/γ-PGA nanoparticles had a particle size of 155.1 ± 7.3 nm with a zeta potential of −23.9 ± 0.9 mV. Moreover, the EGCG/gelatin/γ-PGA nanoparticles enhanced the long-term storage stability and sustained antioxidant activity of EGCG compared to EGCG/gelatin nanoparticles. The nanoparticles protected EGCG in simulated gastric fluid containing pepsin while releasing it in simulated intestinal fluid. Additionally, the amount of EGCG transported in the Caco-2 monolayers treated with EGCG/gelatin/γ-PGA nanoparticles was three times higher than that of free EGCG, which might be related to the paracellular pathway and endocytosis. These results suggest that EGCG/gelatin/γ-PGA nanoparticles might be an effective delivery vehicle for EGCG, enhancing its potential applications in the functional food field.