Preparation And Properties Of Juglans Mandshurica Maxim Calcium-Chelating Peptide

In this study,the isolated protein was extracted from the juglans mandshurica maxim meal after oil extraction,and the protein was isolated by alkaline protease digestion to obtain the juglans mandshurica maxim meal polypeptide and obtain the juglans mandshurica maxim peptide from the isolated protein by using alkalase.The juglans mandshurica maxim calcium-chelating peptide was prepared by juglans mandshurica maxim peptide and the CaCl2 as raw materials.The mechanism and stucture of juglans mandshurica maxim calcium-chelating peptide was explored.Finally,the changes in antioxidant activity of peptides and calcium-chelating peptide after in vitro digestion were examined.The main research contents and results were as follows:(1)The effect of degree of hydrolysis on the antioxidant activity of the juglans mandshurica maxim meal polypeptide was studied.The results showed that as the hydrolysis time increases,the antioxidant activity of the juglans mandshurica maxim protein hydrolysate increases.After 3 h of hydrolysis,the the scavenging capacity for DPPH-was close to 90%,and the scavenging capacity for OH-was 49.3%.(2)The effects of pH,mass ratio of JPH to calcium,reaction time and temperature on the chelation rate of peptide calcium chelate were investigated on the basis of single factor.Then,box-Behnken response surface model was employed to optimize the chelating parameters with chelation rate as an indicator.The optimal conditions for the chelation reaction were:mass ratio of JPH to calcium of 3:1,pH 8,reaction time 40 min,and temperature 45?.The final chelation rate was 67.21%.(3)The structure and properties of peptides before and after chelation were studied.The results suggested that the peptide was aggregated after chelating,and the particle size also increased.The shear viscosity increased compared with that before chelating.The main binding sites for the chelating reaction are-NH2,-COOH and C=O.The result of EDS spectroscopy determination showed that the calcium content of the calcium-chelating peptide was about 14.53%.The binding capacity of calcium ions was related to acidic amino acids and hydrophobic amino acids.(4)Both the bioavailability and antioxidant activity of juglans mandshurica maxim peptide and calcium-chelate peptide were compared.The results indicated that the solubility of inorganic calcium salt decreased significantly with the increase of pH value,and the solubility of peptide calcium chelate decreased slightly,and the antioxidant activity was enhanced after the chelation.The calcium ion dissolution rate was negatively correlated with the pH during in vitro simulated digestion.Additionally,the calcium-chelating peptide after gastrointestinal simulated digestion still retained certain antioxidant activity,and was stronger than the peptide after gastrointestinal simulated digestion.