Study On Preparation,Physicochemical Properties And Bioavailability Of Fiber/Peptide Iron Chelate

Iron is an important micronutrient that plays an important role in many human reactions,such as oxygen transport,electron transfer,gene regulation and cell division.In addition,iron is also an important structural component of cytochrome and various enzymes,and a component of the heme family in hemoglobin and myoglobin,so it participates in and regulates many important physiological processes.Iron deficiency is the most common micronutrient deficiency in the world,affecting about 1.6 billion people,accounting for more than 30 per cent of the world’s population.At present,although there are many kinds of iron supplements on the market,they all have some disadvantages,including some side effects on gastrointestinal tract,low bioavailability and so on.Therefore,there is an urgent need to develop a safe and efficient iron supplement to solve the current situation.In recent years,many food scientists have paid attention to bioactive peptides with mineral binding properties.Compared with the existing iron supplements,bioactive peptides can combine with metal ions by electrostatic interaction to form complexes with higher stability,solubility and bioavailability.Whey protein isolate is the main component of milk and has high nutritional value.Many kinds of peptides with chelating activity can be produced under the action of corresponding enzymes,and protein fibers can be formed by heating whey protein isolate under specific conditions.it has a certain significance for the research,development and application of new iron supplements.In this paper,I use whey protein isolate as raw material,bioactive peptides were prepared by enzymatic hydrolysis,whey protein isolate ferrous chelates were prepared by optimizing enzymatic hydrolysis and chelation reaction,and the chelates were characterized.Whey protein isolate fiber was prepared by heating whey protein isolate and mixed with peptide iron chelate.The stability and bioavailability of fiber/peptide iron chelate were determined by simulated digestion test in vitro and Caco-2 cell experiment.The specific experimental results are as follows:1.The whey protein isolate peptide was prepared by trypsin hydrolysis of whey protein isolate,and the molecular weight distribution of the peptide was determined by high performance liquid chromatography（HPLC）.The results showed that 98.81%of the peptide molecular weight was concentrated below 5 KDa.Taking the chelating activity of peptides as the evaluation index,the enzymatic hydrolysis process and chelating process were optimized.It was determined that the chelating activity of peptides was the highest when the enzymatic hydrolysis time was 4 hours and the mass ratio of peptide to iron was 1:3,which was 38.17μg/m L and 38.78μg/m L,respectively.The peptide iron chelate was characterized by ultraviolet absorption spectrum,Fourier transform infrared spectrum and thermogravimetric experiment.The results of UV spectrum showed that the maximum absorbance of polypeptide solution before and after chelation was blue shifted from 212 nm to 207 nm and the absorption intensity was also increased.The results of Fourier transform infrared spectroscopy showed that the peptides chelated with ferrous ions to produce new substances,and the peptides-COOH,-NH₂and C=O took part in the chelation reaction.Thermogravimetric experiments show that the thermal stability of peptide iron chelates is better than that of peptides.2.Protein fibers were prepared by heating whey protein isolates under specific conditions,and the protein fibers under different heating time were characterized by transmission electron microscope,Th T fluorescence spectrum and ANS surface hydrophobicity.The transmission electron microscope shows that with the extension of incubation time,the morphology of the fiber becomes slender and denser.The results of Th T fluorescence spectrum and ANS surface hydrophobicity showed that the fiber had matured after incubation for about 8 hours.The rheological experimental results of fiber/peptide iron chelates showed that the apparent viscosity,storage modulus（G’）and loss modulus（G’’）of peptide iron chelates increased after adding different concentrations of fiber.This shows that the peptide iron chelate will gradually form gel after adding a certain concentration of fiber.At the same time,the fiber has a certain protective effect on ferrous ions in peptide iron chelate solution.The color of the peptide iron chelate solution with 2%fiber concentration changed after 14 days at room temperature,while the peptide iron chelate solution without fiber changed after 4 days at room temperature.3.The stability of fiber/peptide iron chelate in gastrointestinal tract was verified by simulated digestion experiment in vitro.the results showed that the fiber/peptide iron chelate dissociated in the gastrointestinal tract,but it finally existed in the form of peptide iron chelate.When the chelate just entered the simulated gastric juice,the content of free ferrous ion in the solution increased from 4.14μg/m L to 16.79μg/m L.The content of free ferrous ion in the solution decreased to 2.43μg/m L.The results of CCK8 toxicity test showed that peptide iron chelate and fiber/peptide iron chelate had no toxic effect on the growth of Caco-2 cells,and could promote the growth of Caco-2 cells in a certain concentration range.The results of Caco-2 cell experiment showed that compared with traditional inorganic iron salts,peptide iron chelates and fiber/peptide iron chelates were more favorable for Caco-2 cells to absorb and utilize iron,and fiber could also improve the bioavailability of iron.