Formation Of Preserved Egg Yolk Gelation Induced By Sodium Chloride

Salted eggs,which are a traditional Chinese egg product,are favored by Chinese consumers'and have become very popular in other Asian countries due to their unique‘fresh,fine,tender,loose,gritty and oily texture'features.However,the processes and mechanisms involved in the maturation of salted eggs during salting are unclear.Therefore,this study investigated the impact of NaCl treatment on the gelation behavior of egg yolks and egg yolk proteins were evaluated by means of low-field magnetic resonance(LF-NMR),texture analyzer,rheometer,environmental scanning electron microscope(ESEM),confocal laser scanning microscope(CLSM),transmission electron microscope(TEM)and conventional physicochemical property determination.Changes in the protein conformation and the interaction forces between protein molecules of egg yolk and egg yolk proteins during salting were examined by fourier transform infrared spectroscopy(FTIR),differential scanning calorimetry(DSC),polyacrylamide gel electrophoresis(SDS-PAGE)and chemical methods.The external and internal molecular mechanism of egg yolks and egg yolk proteins coagulation under the effects of higher NaCl treatment was analyzed.It provides a theoretical basis for the quality control of salted egg and the improvement of low salinization process.The main contents and results are as follows:1.The effects of the salting process using a brine solution with different salt concentrations on the physicochemical properties,textural properties,and microstructures of duck eggs were evaluated.The results showed that the effects of salting on the moisture content,pH value,and viscosity and increasing salt content and hardness,and microstructures of duck eggs vary with the salt concentration in the brine solution to a certain extent.Higher salt concentrations in the brine solution lead to higher pH values but lower springiness and viscosity of the raw egg whites.Heating treatment can lower the moisture content in both the egg yolks and egg whites,increase the oil exudation and hardness of the egg yolks,and decrease the springiness and pH value of the egg yolks.The brine solutions concentration of20%to get better quality salted egg.2.Changes in the protein conformation and the interaction forces between protein molecules of salted egg yolk were examined by newer techniques and chemical methods during salting.Results indicated that as the pickling proceeded,the soluble protein content and free sulfhydryl content of raw salted egg yolks,the free sulfhydryl content and surface hydrophobicity of cooked salted egg yolks showed an overall increasing trend,followed by significant decrease.The surface hydrophobicity of raw salted egg yolks exhibited an increasing trend.(DSC)results demonstrated that salting can stabilize the protein molecules by an increase in denaturation temperatures.Fourier transform infrared spectroscopy(FTIR)revealed that the secondary structures of egg yolk proteins underwent changes,but no difference in protein patterns of either raw or cooked salted egg yolks was observed by SDS–PAGE during pickling3.We aimed to investigate the impact of NaCl treatment on the gelation behavior of egg yolks,plasmas and granule has been assessed.Results indicated that as the pickling proceeded,the NaCl content and oil exudation of egg yolks,plasmas and granules showed an overall increasing trend.The moisture content of egg yolks,plasmas and granules exhibited a decreasing trend.The size of the particles(TEM)and soluble protein content increased of egg yolk and plasma,the surface hydrophobicity of egg yolk and granules increased,followed by decreased.The egg yolks and plasmas of salted for 2d are larger than those of fresh egg yolks and plasmas,which was consistent with the soluble protein increase.The egg yolks,plasmas and granules in the later of salting were disrupted and liberated constitutions(phospholipids,neutral lipids and proteins)randomly aggregated.These aggregates corresponded well with the T₂₁ and T₂₂ related to lipid protons decrease.4.Low-density lipoprotein was induced to form a gelation by NaCl using the same system and techniques methods in the previous chapters evaluated its gelling mechanisms.The low-density lipoprotein gels microstructure presented multiple aggregate structures in which filamentous apoproteins and some non-spherical proteins and fat particles interweave together.First,intermolecular low-density lipoproteins are involved in protein aggregation via intermolecular disulfide bond.Second,the intramolecular low-density lipoproteins were disrupted and released constituents(phospholipids,neutral lipids and proteins)associated with each other generated huge aggregates with multiple aggregate structures via hydrophobic interactions.Through comparison with the physicochemical properties of the previous chapter,we proved that the salting effect of NaCl increased the release of free lipids mainly due to the structural changes in the low-density lipoproteins.Granule plays a role in the formation of aggregation gel of salted egg yolk,which has higher hardness texture.