Preparation And Properties Of Soybean Peptide Zinc Chelate And Soybean Peptide Ferrous Chelate

Soy is one of the most important food crops in the world.It has been grown for over 7,000 years.It is native to China and is grown all over the world.China is the world’s largest importer of soybeans.The main processed products of soybeans are soybean oil and soybean meal.With the competitive pressure on traditional industries and the increase in industrial concentration,promoting deep processing of soybeans and increasing the added value of soybeans is an inevitable trend in the development of the soybean industry.Both zinc and iron are essential inorganic mineral elements for human growth,development and maintenance of health.Zinc deficiency may lead to developmental disorders,anorexia,pica,skin damage and other diseases.Iron deficiency is likely to lead to iron deficiency anemia.Traditional zinc and iron supplements often have defects such as low absorption and utilization rate and toxic and side effects.Peptide metal chelates can effectively solve these problems.Soybean is a high quality and relatively inexpensive source of protein with all essential amino acids.The nutritional value of soy protein is close to that of animal protein with high biological value and is a good choice for the preparation of peptide metal chelates,however,it is still unclear how soy peptides and zinc and ferrous iron are bound.Therefore,in this paper,we prepare soybean peptides from soybean protein,prepare soybean peptide chelated zinc and soybean peptide chelated ferrous iron,and study and compare the structure,characterization and properties of peptide chelated zinc and peptide chelated ferrous iron,in order to provide constructive reference for the high value utilization of soybean resources.The main research contents and results are as follows.（1）To explore the preparation process of soybean peptide zinc chelate.The preparation process was optimized by single factor experiment and orthogonal experiment,and the optimal chelation conditions were obtained as follows:temperature60℃,time 60 min,p H 6.0,zinc acetate dihydrate concentration 1.6%,substance mass ratio 8:1（soybean peptide:zinc acetate dihydrate）,and the zinc ion chelation rate was62.40%under this condition.The soybean peptide chelate zinc prepared under the optimal conditions was subjected to graded alcohol precipitation,and it was found that it could be dissolved in 70%ethanol aqueous solution,and the peptide chelate zinc precipitated in 80%ethanol aqueous solution had the highest zinc content,reaching80.21 mg/g.（2）To explore the preparation process of soybean peptide ferrous chelate.The preparation process was optimized by single factor experiment and orthogonal experiment,and the optimal chelation conditions were obtained as follows:temperature40°C,time 40 min,p H 6.0,ferrous chloride tetrahydrate concentration 0.4%,substance mass ratio is 5:1（soybean peptide:ferrous chloride tetrahydrate）,and the chelation rate of ferrous ion is 73.94%under this condition.The soybean peptide chelate zinc prepared under optimal conditions was subjected to fractional alcohol precipitation,and it was found that it could be dissolved in 70%ethanol aqueous solution,and the peptide chelate zinc precipitated in 80%ethanol aqueous solution had the highest ferrous content,reaching 144.80 mg/g.（3）To analyze and compare the infrared spectrum,microstructure,molecular weight distribution,amino acid composition and amino acid sequence of soybean peptide,peptide zinc chelate and peptide ferrous chelate.Infrared spectroscopy found that-NH,CH₂,C-N,C=O,-COO-participated in the chelation reaction with metal ions in the chelation reaction of soybean peptide with zinc and ferrous iron.The results of scanning electron microscopy showed that the combination of zinc and ferrous ions with soybean peptides would lead to intramolecular and intermolecular folding and aggregation of soybean peptides,and the microstructures of peptide chelated zinc and peptide chelated ferrous were significantly different.Molecular weight analysis revealed that the molecular weight of the peptide chelates obtained by alcohol deposition increased with increasing ethanol concentration,and the molecular weights of both zinc chelate with the highest zinc content and ferrous iron chelate with the highest ferrous iron content were concentrated between 150-500,and the molecular of ferrous iron chelate with soybean peptide was smaller.The results of amino acid analysis showed that soybean peptides containing acidic or basic amino acid residues were more likely to chelate with zinc and ferrous ions.The results of UPLC-Q-TOF-MS showed that the small peptide composed of 2-3 amino acids has dual chelating activities of zinc and ferrous iron.In addition,phenylalanine may play a role in the chelation of 2-3 small peptides and metal ions in the process important role.（5）Study the dissolution rate of zinc and ferrous ions of soybean peptide zinc chelate and soybean peptide ferrous chelate at different p H values,and found that at the neutral p H value,peptide zinc chelate and peptide ferrous chelate compounds have higher solubility.The results of in vitro simulated digestion experiments showed that the peptide chelates could maintain good solubility in the presence of pepsin and trypsin.The results of antioxidant experiments showed that soybean peptides and zinc ions still retained antioxidant activity after chelation,and the antioxidant activity was positively correlated with the concentration.