Tea pomace protein-ε-polylysine-anthocyanin composite nanocomplexes: Elucidation of stability, structural properties, and in vitro digestion

Nano-complexation with food proteins has been well recognized to be an effective and safe strategy to improve stability and bioavailability of bioactive compounds. In this study, we applied tea pomace protein (TP) and ε-polylysine (PLL) to load anthocyanins (ACNs), which were further characterized by scanning electron microscopy (SEM), fourier transformed infrared spectroscopy (FTIR), and fluorescence spectrum (FS). The stability and digestive characteristics in vitro were also investigated. The result showed that ACNs-loaded TP-PLL nanocomplexes (TPPLA) formed a dense three-dimension crosslinked network structure by interactions between TP and PLL, while the flakes of ACNs were dispersed in the grid. The interactions between nanocomplexes were analyzed by molecular docking and found to be mainly through hydrogen bonds on polyphenols (C3G) or electrostatic interactions in the hydrophobic cavities of TP (11 S). Compared with free ACNs, The TPPLA nanocomplexes improved its encapsulation efficiency (63.63 ± 0.50 %) and thermal retention rate (70.18 ± 0.98 %). And they presented excellent properties of controlled release during the simulated digestion in vitro. This study is the first to propose developing and utilizing tea pomace protein as a microencapsulated material and the result may promote the successful application of TPPLA nanocomplexes in foods and nutraceuticals.