Development Of Corn Yogurt Containing Antioxidant Peptides And Its Functional Research

Oxidative stress can cause cell damage and cause many diseases.The body has a certain oxidation regulation system to maintain the balance of free radical metabolism;when the body's own defense system cannot resist the damage caused by free radicals,it needs exogenous antioxidants to resist and alleviate.Antioxidant peptide is a kind of bioactive peptide with antioxidant function derived from protein hydrolysis.In recent years,more and more scholars have studied the source,preparation and functional properties of antioxidant peptide.In this experiment,a strain of lactic acid bacteria with high production of antioxidant peptides from fermented milk protein was screened,and its physiological characteristics were studied;the preparation conditions of corn enzymatic hydrolysis fermentation broth and yogurt fermentation were optimized to prepare corn yogurt rich in antioxidant peptides;The mouse experiment proved the antioxidant capacity of corn yogurt rich in antioxidant peptides,aiming to provide a theoretical basis for the development and utilization of functional yogurt.Finally,the antioxidant peptide contained in the yogurt was separated,identified,and synthesized to verify its antioxidant activity.The main research results are summarized as follows:1.A lactic acid bacteria strain producing antioxidant peptides from fermented milk protein was screened,The content of peptide in yoghurt fermented by this strain was 0.580 ± 0.018 mg/ml,and the total antioxidant activity was equivalent to0.348±0.005 mM Trolox equivalent.After observing the colony morphology,Gram staining and 16 S rDNA sequence molecular analysis,the strain producing antioxidant peptide was Lactobacillus fermentum.It grew well in low pH environment,and was well tolerated in MRS medium containing different concentrations of NaCl.Its survival rate was higher than 60.0% after growing in simulated artificial stomach and intestinal juice environment for 4 hours,and the genetic stability of antioxidant peptides produced by fermented milk protein was good.2.After single factor,response surface optimization and orthogonal optimization experiments,the best enzymatic hydrolysis scheme for corn is obtained as follows:substrate concentration is 9.82%,enzyme amount is 6.53%,pH = 9.19,temperature is49.53 ?,under these conditions The degree of hydrolysis of the corn enzymatic hydrolysate is 30.60±0.11%.The best plan for Bacillus subtilis fermentation is:inoculum amount is 6%,fermentation time is 18 h,initial pH is 8,fermentation temperature is 37?,and total antioxidant activity of fermentation broth is0.748±0.016 mM Trolox equivalent.The optimum conditions for preparing corn yoghurt containing antioxidant peptide were as follows: the addition amount of the enzymatic fermentation broth is 9%(v/v),the first starter(Lactobacillus fermentum)is 3%(v/v),and the second The addition amount of starter(direct throw starter)is 2%(v/v),and the addition amount of sucrose is 8%(w/v).The peptide content of the obtained yogurt is 0.914±0.009 mg/ml,and the total antioxidant activity is equivalent to the 0.781±0.020 mM Trolox equivalent,and the quality is good.3.The prepared corn yogurt with antioxidant peptides was given to the aging mice induced by subcutaneous injection of D-galactose.The liver tissue of mice was taken out for HE staining,and the related oxidative stress indexes in the liver of mice were determined.The results showed that corn yoghurt containing antioxidant peptides could effectively alleviate the oxidative stress of aging mice induced by D-galactose.The specific performance is as follows:functional yogurt can significantly reduce the infiltration degree of inflammatory cells in D-galactose-induced aging mice,significantly increase T-AOC,SOD activity,CAT activity,GSH content,NO content in liver of D-galactose-induced aging mice,and significantly reduce MDA content,ROS content,LDH activity,ALT activity and AST activity.It can also significantly inhibit the release of tumor necrosis factor TNF-? and inflammatory factors IL-6 and IL-1?.4.Four different antioxidant peptides from corn yogurt with antioxidant peptides were isolated and identified by ultrafiltration,gel chromatography and mass spectrometry.They are FPKYPVEPF,HLPLPLLQSWM,IGGIGTVPVGR,and LTVTVTVTPGSR.Among them,FPKYPVEPF and HLPLPLLQSWM are from milk protein,and IGGIGTVPVGR and LTVTVTVTPGSR are from corn protein.The identified peptide sequences were synthesized to verify their antioxidant activity.It was found that the DPPH free radical scavenging rates of the four peptides were all above 60.0%,and the total antioxidant activity reached the 0.6mM Trolox equivalent.The total antioxidant activity of HLPLPLLQSWM is close to 0.75 mM Trolox equivalent,which is significantly higher than the other three peptides.In summary,the yogurt prepared by the combination of lactic acid bacteria with high antioxidant peptide content and optimized corn enzymatic fermentation broth screened in this topic has high antioxidant peptide content and good taste.In addition,it can significantly relieve the aging of mice induced by D-galactose.Finally,four peptides with different sequences and good antioxidant activity were obtained in the prepared yogurt.