The Mechanism Of Post-Haze Caused By The Interaction Of Apple Glycoprotein With Polyphenols In Apple Juice

In this paper,the interaction between apple glycoprotein and chlorogenic acid,quercetin,tannic acid,and catechin was analyzed by fluorescence spectroscopy.The quenching mechanism,the number of binding sites,the binding constant,and the type of binding force are determined.Spectrophotometry was used to verify the effect of polyphenols on the haze of the system.Polyphenols that can increase haze were match in pairs,and explored the interaction mechanism of two polyphenols with glycoproteins.The lectin chip and mass spectrometry were used to analyze the glycan structure of glycoproteins,which provided ideas for the structural identification of glycoproteins and the study of post-haze mechanisms.The result shows that the binding of chlorogenic acid to maloprotein was a static quenching process,and that of tannic acid and quercetin were dynamic and static binding quenching processes.With the increase of temperature,the binding stability of chlorogenic acid and glycoprotein decreased,and tannic acid and quercetin did the oppsite.In the interaction between chlorogenic acid and glycoprotein,?G<0,?H<0,?S<0,and the main forces were hydrogen bonding and van der Waals force.In the interaction between tannic acid,quercetin and glycoprotein,?G<0,?H>0,?S>0,and the main force was hydrophobic action.All three polyphenols increased the haze of the system.Catechin reduced the hydrophobicity of apple glycoprotein and did not increase the haze of the system.In two polyphenols system,chlorogenic acid and quercetin reduced the affinity of each other with glycoproteins,and the addition of the two hardly changed the haze of the system.The addition of tannic acid hardly changed the affinity of glycoprotein and quercetin,but weakened the haze stability of the system.The addition of quercetin had few effect on the haze of the "tannic acid-glycoprotein" system.In the two polyphenols systems of chlorogenic acid and tannic acid,both increased their affinity for glycoproteins.The addition of 1 ?M chlorogenic acid increased the quenching rate to 27.10%,39.55%,49.20%,59.85% and 66.80%.The haze increased to 0.111,0.117,0.134,0.155,0.162 and 0.172;the addition of 0.005 ?M tannic acid increased the quenching rate to 34.05%,40.44%,50.51%,57.72% and 65.62%,and the haze changed to 0.097,0.117,0.132,0.144,0.151,and 0.164.Monosaccharides and glycans such as N-acetylglucosamine,N-acetylgalactosamine-linked O-glycans,and high-mannose types were presented in glycoproteins.A total of 25 N-glycans were obtained by mass spectrometry,including 18 pentasaccharide core glycans,among which,three was high-mannose type,ten was complex type,and five was hybrid type.This study clarified the mechanism of interaction between apple glycoprotein and polyphenols to cause post-haze,clarified the structural characteristics of glycans of glycoproteins that affected post-haze,and enriched the basic theory of food-derived glycoproteins.