Preparation process optimization, structural characterization and in vitro digestion stability analysis of Antarctic krill (Euphausia superba) peptides-zinc chelate

•The preparation process of Antarctic krill peptides-zinc chelate was optimized.•Chelating sites were carboxyl oxygen and amino nitrogen atoms of the peptides.•Differences of characterization between peptides and peptides-zinc chelate were given.•Chelate showed excellent stability against to various pH and gastrointestinal digestion. In the study, a novel kind of peptides-zinc (AKP-Zn) chelate was obtained using the Antarctic krill (Euphausia superba) peptides (AKP) as raw material, the reaction was carried out with the mass ratio of the AKP to ZnSO4·7H2O of 1:2 at pH 6.0 and 60 °C for 10 min. The structure and composition of the AKP, including particle size, Zeta potential, molecular weight distribution, amino acid composition, microstructure and surface elemental composition, changed significantly after chelating with zinc. The result of Fourier transform infrared spectroscopy indicated that zinc could be chelated by carboxyl oxygen and amino nitrogen atoms of the AKP. Furthermore, compared with zinc sulfate and zinc gluconate, the AKP-Zn chelate was more stable at various pH conditions and the simulated gastrointestinal digestion experiment. These findings would provide a scientific basis for developing new zinc supplements and the high-value utilization of Antarctic krill protein resource.