Abstract: The microstructure of whey protein (WP)/cyanidin-3-O-glucoside (C3G) nanoparticles was studied by a nanometer particle size analyzer, transmission electron microscopy and Fourier transform infrared spectrometry, and the digestion stability in vitro and storage stability were analyzed as well. Nanoparticles with an average diameter of (275.51 ± 3.15)nm, PdI of (0.28 ± 0.01), zeta potential of (?16.92 ± 1.04) mV, encapsulation efficiency of (97.09 ± 2.39)% and loading efficiency of (2.43 ± 0.05)% were prepared successfully under the following conditions: heating WP in a water bath at 80 ℃ for 30 min, homogenously mixing it with C3G: WP at a volume ratio of 1:80 after pH adjustment to 7, and finally adding 8 mmol/L CaCl2. Transmission electron microscopy showed that after encapsulating C3G, the nanoparticles changed from hollow nanospheres to typical “core-shell” structures. The results of infrared spectroscopy showed that the secondary structure of whey protein was changed after binding with C3G; the contents of α-helix and β-turn were reduced, while the contents of β-sheet and random coil were increased. After in vitro digestion, the release rate of C3G from the WP-C3G nanoparticles was (87.25 ± 3.72)%, and the degradation rate of C3G decreased by (51.34 ± 0.52)% as compared with free C3G. After being stored for 20 days in the dark, the retention rate of free and encapsulated C3G were (42.62 ± 2.33)% and (64.14 ± 1.70)%, respectively. The results showed that the gastrointestinal digestion stability and storage stability of C3G can be effectively improved after being encapsulated with whey protein.

Key words: whey protein, cyanidin-3-O-glucoside, nanoparticles, in vitro digestion