| Antioxidants are a class of substances that can inhibit the peroxidation of biological macromolecules or scavenge free radicals in the body,thereby eliminating the damage of free radicals to the human body.Antioxidant peptide is a kind of antioxidant.It is a small biological active peptide obtained by hydrolyzing animal and plant proteins.It has the advantages of low toxicity,harm lessness and wide sources.The research team prepared the British red kidney bean protein antioxidant peptide with good antioxidant activity in the early stage,but the activity was lower than the current synthetic antioxidants used in the food industry.In order to further improve its antioxidant activity,the lyophilized powder of antioxidant peptides was used as a raw material for glycosylation reaction with xylose.First,the optimal reaction conditions for glycosylation modification were determined;secondly,the properties of glycosylation modified products were analyzed by fluorescence spectroscopy,ultraviolet spectroscopy,Fourier mid-infrared spectroscopy,SDS-polyacrylamide gel electrophoresis and in vitro gastrointestinal simulated digestion;finally,the functional properties of the glycosylated products were determined and analyzed.It provides a theoretical basis for the better application of British red kidney bean antioxidant peptide glycosylation modified products in the modern food industry.The results of the study were as follows:1.Optimal glycosylation modification conditions for British red kidney bean antioxidant peptidesThe optimal reaction conditions of glycosylation modification were determined through single factor experiment,orthogonal experiment,and verification experiment.The results showed that the p H of the reaction solution has the greatest influence on the hydroxyl radical scavenging ability of the glycosylation modified product when the reaction temperature was 90℃,and the reaction time had the greatest effect on the content of acrylamide in the reaction product.The optimal reaction conditions for glycosylation modification were:under the condition of glycosylation reaction temperature of 90℃,the concentration of antioxidant peptide in the reaction system was 10 mg/m L,p H 7,reaction time 4 h,glycopeptide ratio 1:1.The yield of the glycosylation modified product prepared under these conditions was 98.6%,and the scavenging rate of hydroxyl radical,DPPH free radical,reducing power and ferrous ion chelating ability were significantly improved compared with those before the modification.The acrylamide production was as low as 359.23μg/L,which was close to the industry standard for acrylamide content in China;the chelating ability with ferrous ion was higher than that with vitamin C at the same concentration,which was probably due to the fact that the glycosylation modified product of the British red kidney bean antioxidant peptide contains more chelating groups with ferrous ions,so it is an ideal metal chelating agent that can inhibit oxidation of substances in the food system.2.Analysis of glycosylation modification products of antioxidant peptides from British red kidney beanThe browning degree,grafting degree,particle size distribution,and Zeta potential of the glycosylation products were measured,and fluorescence spectroscopy,ultraviolet spectroscopy,Fourier mid-infrared spectroscopy,SDS-polyacrylamide gel electrophoresis were analyzed.The test results showed that under the optimal reaction conditions,the degree of browning was 0.52,the degree of grafting DG%was 39%,and the particle size distribution decreased and the particle size distribution was between 100 nm and 300 nm after the reaction;the absolute value of the Zeta potential increased from 23.3 m V to 36.6 m V for the kidney bean antioxidant peptide.Through the fluorescence spectrum analysis,it was found that the maximum absorption peak of the antioxidant peptide before the reaction was around 413 nm and the maximum fluorescence intensity was 3761,,and the maximum absorption peak of the modified reaction product was at417 nm and the maximum fluorescence absorption intensity reached 12806.The fluorescence absorption intensity of the modified product was significantly higher than that of the kidney bean antioxidant peptide,which proved that the glycosylation reaction between the kidney bean antioxidant peptide and xylose occurred and produced fluorescent substances.The analysis of ultraviolet absorption spectroscopy showed that the absorption peak of the reaction product had a blue shift,and the ultraviolet absorption intensity at 265-275 nm increased;the analysis of infrared absorption spectra showed that there was stretching vibration absorption at 3373.26 cm-1 and2926.53 cm-1,at the same time,the deformation vibration occurred on N-H bond,and the amide I zone changed at 1663.74 cm-1.It showed that the C=O stretching vibration was generated during the glycosylation modification of the brassica antioxidant peptides.The changes in this interval were found at 1597.64 cm-1 and 1412.46 cm-1,respectively,which were mainly due to the C-N stretching and N-H changes;The SDS-polyacrylamide gel Analysis of the electrophoresis pattern revealed that the band color of the modified glycosylation product was lighter than that of the antioxidant peptide,which was due to the reduction of the free amino group content in the reaction product after the glycosylation reaction.3.Analysis of functional properties of modified glycosylation productsThe analysis of the functional properties of the British red kidney bean antioxidant peptide and the glycosylation modified product showed that the glycosylation modified product has different levels of improvement compared with the kidney bean antioxidant peptide.The measurement results of various functional properties of the glycosylated modified product are as follows,except for water absorption,other indicators have been improved:solubility increased by89.9%,foaming property and foaming stability increased by 51.7%and 25.4%,emulsification properties and emulsion stability increased by 29.8%and 42.5%,oil absorption increased by52.8%,but water absorption decreased by 22.5%,and viscosity increased by 25%.The free sulfhydryl content increased by 65.6%,and surface hydrophobicity increased by 150.9%.4.In vitro gastrointestinal simulated digestion analysisAfter the in vitro gastrointestinal tract simulated digestion,the in vitro antioxidant activities of the glycosylation modified products were all significantly（P<0.05）increased compared to those before modification.After simulating gastric digestion in vitro,the hydroxyl radical scavenging rate,DPPH free radical scavenging rate,reducing power and ferrous ion chelating ability were significantly increased by 66.0%,44.8%,118.5%and 49.0%,respectively;after in vitro simulated intestinal digestion,those parameters significantly increased by 51.5%,36.2%,128.2%and 46.0%,respectively.The antioxidant capacity of the modified glycosylation product was close to that of vitamin C at the same concentration.The anti-oxidant activity of the modified product was further improved by simulated digestion in vitro,and its anti-oxidant activity was not affected after passing through the digestive tract.Thus,indicating that the glycosylated modified product has good antioxidant stability.The above results indicated that the functional properties of British red antioxidant peptide after glycosylation modification have been further optimized,which broadens the use environment and applications of glycosylation modified products with high application potential.It provides a theoretical basis for the early application of glycosylation modified products in food industry.. |
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