Intervention Mechanism Of Catechin On ?-conglycinin Oxidation Induced By Lipoxygenase-catalyzed Linoleic Acid

Soybean was rich in nutrients,which was one of the important sources of human ideal protein.However,LOX can catalyze the lipid peroxidation reaction of residual lipid,which lead to the oxidation of soybean protein,reducing the function and nutritional value of protein.The purpose of this paper was to explore the intervention mechanism of catechin on?-conglycinin oxidation induced by lipoxygenase-catalyzed linoleic acid,lay a theoretical foundation for the controling of soybean protein oxidation,provide theory and guidance of soybean protein control.?1?The load rate of 7S and four kinds of phenolics?caffeic acid,chlorogenic acid,catechin and quercetin?was studied,fluorescence spectrum method was used to study the four kinds of phenolics and 7S interaction,ABTS,ORAC methods was used to evaluate the promotion of 7S antioxidant activity with four kinds of phenolics.A dynamic drop shape analysis method was used to explore the interfacial tension and interfacial film expansion rheological properties of7S-C compounds in safflower seed oil/water boundary and the effect of 7S-C complex on interface absorption characteristics of 7S.A emulsion system was established to catalyze oxidation by adding LOX,which was composed of red flower seed as oil phase and had 7S-C compound as emulsifier,the effect of 7S-C complex on the oxidation stability of the emulsion was studied.The results showed that the heating treatment significantly improved the affinity of 7S to plant phenolics and antioxidant activity of 7S.Compared to caffeic acid and quercetin,catechin and chlorogenic acid had a higher affinity with 7S.The antioxidant activity of 7S significantly increased by phenolics,and the antioxidant capacity of the 7S-phenolics complex was from strong to weak:catechins>quercetin>chlorogenic acid>caffeic acid.Hydrophobic interaction and hydrogen bond force are important forces in the interaction between four phenolics and 7S.The interaction between 7S and catechin had no significant effect on the interface characteristics and emulsification of 7S.The H-7S-C complex can increase the stability of the emulsion by inhibiting the lipid oxidation,the formation of protein carbonyl and the loss of sulfhydryl group.?2?The LOX-LA simulated oxidation system was established to induce the oxidation of 7S.Catechin-protein complexes improved the antioxidant activity of 7S,investigating the effect of catechin-protein interaction on the inhibitory effect of 7S oxidation induced by lipoxygenase-catalyzed linoleic acid.A model of gastrointestinal digestion in vitro was established to study the effect of catechin-protein interaction on the LOX-mediated reduction of protein bioavailability.The results showed that catechin-protein interaction effectively inhibited the lipid and protein oxidation in the LOX-LA oxidation system.It was harder to be digested for7S after oxidation,biological accessibility was lower,the higher the degree of oxidation had the lower biological accessibility,heating can improve the digestibility of 7S in the stomach,catechin-protein interaction can improve the accessibility of oxidative protein.The content of essential amino acids and the kinds of active peptides in 7S were reduced after oxidation.Heat treatment and catechin-protein interaction can improve the nutritional characteristics of oxidative protein after digestion,release more essential amino acids and antioxidant peptides,ACE inhibitory peptides and dipeptide peptidase?inhibitory peptides.?3?The LOX-LA simulated oxidation system was established to induce 7S oxidation.In the initiation of oxidation reaction,catechin was added to the system to investigate the inhibitory effect of catechins on the oxidative inhibitory effect of LOX on 7S.Four kinds of plant phenolics containing catechol structure?caffeic acid,chlorogenic acid,catechin,quercetin?was studied to clear its inhibition mechanism of LOX based on Linweaver-Burk mapping method and fluorescence spectrometry.The results showed that catechins inhibited the oxidation of lipid and protein by inhibiting LOX activity in the LOX-LA oxidation system.The IC₅₀ of LOX inhibitory activities of four kinds of phenolics value were:quercetin?127.21 microns?<catechin?143.34 microns?<caffeic acid?165.51 microns?<chlorogenic acid?179.70 microns?,flavonoids containing catechol structure?catechin and quercetin?had better LOX inhibitory effect than phenolic acid compounds?chlorogenic acid and caffeic acid?.Catechin and quercetin were non-competitive inhibitors of LOX,and chlorogenic acid and caffeic acid were LOX's non-competitiveinhibitingdominatedcompetition-non-competitivehybrid inhibitors.Chlorogenic acid,caffeic acid,catechin and quercetin can cause fluorescence quenching reaction of LOX.The inhibitory activity of phenolics on LOX not only depended on the affinity of phenolics and LOX,but also depended on the binding site of phenolics and LOX.The low concentrations of catechin and quercetin were synergistic.