Explored The Change Mechanism Of Nutrients In Yolk Powder Processing Based On Food Omics Analysis

The yolk is rich in lipids and protein.During heat treatment,egg yolk proteins are denatured,degraded or covalently cross-linked due to high temperature,and lipids are easy to oxidize during heating.Focusing on the protein in yolk,the potential cross-linking aggregation of the glycosylated modified structure after translation in the process of hot processing was focused,and combined with the changes in the functional characteristics of yolk,the molecular structure basis of the influence of hot processing on the characteristics of yolk was comprehensively expounded.Aiming at the lipid in egg yolk,the effects of hot processing on fatty acid composition and molecular structure of lipid in egg yolk were comprehensively analyzed through fatty acid analysis and quantitative comparative analysis of lipid groups.On this basis,the metabolite composition in egg yolk was further taken as the object to explore the mechanism of nutrient changes from the aspects of oxidation index measurement and metabonomics analysis.These changes significantly affect the processing characteristics of egg yolk.Taking fresh egg yolk(F-EY)as the reference,the potential cross-linking aggregation of protein glycosylation modified structure of spray-dried egg yolk powder(SD-EY)in the process of hot processing,the changes of functional characteristics of egg yolk and the molecular structure mechanism of hot processing affecting the characteristics of egg yolk were comprehensively investigated.The results showed that compared with F-EY,the properties of P-EY did not change significantly,while the thermal gel hardness,water holding capacity and emulsifying activity of SD-EY decreased significantly by35.73±3.3%,1.86% and 48.72%,respectively.The surface hydrophobicity of SD-EY was significantly decreased,and the content of free sulfhydryl group and Zeta potential were significantly increased(p < 0.05).The results of electrophoresis showed obvious cross-linking of proteins in SD-EY.Quantitative N-glycosylation proteomic analysis showed that compared with F-EY,there were 2 up-regulated n-glycosylation sites and 21down-regulated n-glycosylation sites in SD-EY.The main N-glycoproteins mainly include APOB,vitellogenin,riboflavin binding protein,etc.,which cross-linked and accumulated at high temperature,resulting in the downregulation of 9 n-glycosylation sites(p < 0.05),affecting the distribution of proteins and lipids in the yolk system,and resulting in changes in the processing characteristics of yolk.Among them,APOB is a potential key protein that changes yolk characteristics during spray drying.Egg yolks are rich in lipids,which are easily altered during processing and storage.In this study,liquid chromatography-tandem mass spectrometry(LC-MS)strategy was used for quantitative lipid omics analysis of egg yolks after spray drying(SEY)and accelerated storage(S-SEY).Spray drying causes lipid oxidation(especially of free fatty acids),potential hydrolysis of phospholipids and changes in the form of some polyunsaturated fatty acids(DHA,EPA,linolenic acid and ARA)in egg yolk.The accelerated storage process is further exacerbated by lipid changes caused by the spray drying process.Specifically,lipid oxidation increased after storage,and the abundance of certain phospholipids,such as PA and PE,significantly decreased,as did the abundance of polyunsaturated fatty acids that form triglycerides.These results provide new insights into the mechanism of egg yolk performance changes during spray drying and storage,and provide valuable reference data for the application of egg yolk powder in food processing.Metabolites of freeze-dried egg yolk powder(FEY),spray dried egg yolk powder(SEY)and spray dried egg yolk powder after storage(S-SEY)were analyzed by means of broad target metabolomics.A total of 1032 metabolites were identified.Next,OPLS-DA model was established according to the identified metabolites to screen out the differential metabolites among the groups.Studies have shown that the main metabolites of change are amino acids and their metabolites,lipids,acyl lipids and vitamins.During storage,metabolites are further decomposed and organic acids and their derivatives are increased.The results showed that the abundance of amino acids and glycerophospholipids increased and the abundance of sugars decreased due to the combination of protein denaturation,fat oxidation and Maillard reaction at high temperature.In addition,the beneficial amino acids and vitamins produced in the processing of egg yolk powder will improve the nutritional value of egg yolk,and also contribute to the storage of egg yolk powder.This study further illustrates that metabolomics can search for the molecular details that make food unique,identify the bioactive ingredients in food,and better understand their potential beneficial or harmful consequences.The topic is expected to discover the difference changes of protein,lipid and metabolite of main nutrients in egg yolk after hot processing,and to clarify the change mechanism.The research results will provide key information for understanding the mechanism of egg yolk hot processing and the molecular mechanism of egg yolk preservation.