Preparation process optimization of pig bone collagen peptide-calcium chelate using response surface methodology and its structural characterization and stability analysis

•Alcalase and neutrase were used for preparing calcium-binding peptide from pig bone.•The chelating conditions was optimized by response surface methodology.•The differences of characterization between peptide and peptide-calcium chelate were given.•The stability of chelate against to pH, temperature and gastrointestinal digestion was evaluated.•Peptide-calcium chelate could significantly improve calcium transport in Caco-2 cell monolayer.