Preparation Of Glutamine Peptide From High Substrate Concentration Of Wheat Protein And Its Intestinal Repair Function

Glutamine?Gln?is an important energy source for intestinal cells.Wheat protein is rich in Gln,which is an ideal material for producing peptides with high content of Gln.However,the low substrate concentration and complex process limit the industrialization of wheat peptide.In this research,we investigated the preparation technology of wheat glutamine peptide at high substrate concentration and its intestinal repair activity was studied.Powdered drinks contained wheat peptide were developed in order to broaden the application fields of wheat protein.In this research,the hydrolysis effects of six kinds of representative plant protein proteases for wheat protein at high substrate concentration were detected.By considering the short peptide yield and enzyme cost,the XS was determined as the main enzyme.On this basis,Protamex and Alcalase which can greatly improve the flavor and yield of hydrolysates were used to the compound enzymatic hydrolysis of wheat protein respectively.By studying the dosage and hydrolysis time,the preparation technology of wheat peptide with two or three enzymes was determined.A?double enzymes?process:XS?1%?+Protamex?0.25%?;B?three enzymes?process:XS?1%?+Protamex?0.25%?+Alcalase?0.30%?.In the A process,XS and Protamex were added synchronously without adjusting the pH of the system.In the B process,the first step was to add XS and Protamex,and after 3 h reaction at natural pH,Alcalase was added after adjusting pH to 8.5.In the two processes,the substrate concentration was 25%,the hydrolysis temperature was 50?,and the total hydrolysis time was 6 h.Compared two preparation processes,the enzymatic hydrolysate yield,short peptide content,and oligopeptide content of the B process were significantly higher than those of the A process.However,the wheat peptide prepared by the A process had higher content of Gln and lower bitterness degree.Secondly,the effects of two kinds of wheat peptides?A-double enzymatic hydrolysis products;B-three enzymatic hydrolysis products?and their digestion in vitro on oxidative stress injury induced by H₂O₂ in Caco-2 cells were studied.The result showed that wheat peptides A and B could alleviate the decrease of cell survival rate,and reduce the degree of cells damage.Both of peptide A and B still showed this effect after digestion in vitro,but the digestion of wheat protein showed no effect on the cell survival rate.Antioxidant index,including CAT,GSH,SOD and MDA of cell lysates in each group were measured.The result indicated that peptide A and B both improved the cellular antioxidant capacity,with an increase of intracellular GSH and decrease of lipid oxidation of damaged cells.The peptide A still had these function after digestion in vitro,but peptide B had no effect on the cellular antioxidant capacity and the level of GSH of damaged cells after digestion in vitro.This indicated that some active fragment in peptide B might be damaged after digestion.In addition,although the digestion of wheat protein could reduce the lipid oxidation of damaged cells,it had no effect on the cellular antioxidant capacity and the level of GSH.Thirdly,the effects of peptides A and B on colon inflammation in UC mice induced by DSS were studied.Mice were allowed to drink for 5 days with a 3%DSS solution to cause colitis,and with wheat peptide samples rich in Gln for gavage.The changes of body weight,DAI score,colon length,histological status,MPO level,antioxidant capacity,and inflammatory cytokine level were studied.The results showed that peptides A and B significantly relieved the intestinal inflammation induced by DSS,which could alleviate the colon mucosal inflammation,reduce the damage degree of colonic mucosa,and enhance antioxidant ability of mice colon tissue.The effect of peptide A was better than that of peptide B.Finally,common and sugar-free wheat peptide solid beverages were developed,which can both meet the sensory and nutritive requirements.The amino acid composition of wheat peptides was adjusted by adding appropriate amino acids.The protein content of sugar-free type was about 80%,while the protein content of common type was about 60%.