Effects Of Metal Ions On Formation Of Preserved Egg White Gel Induced By Strong Alkali

The preserved egg is a traditional egg product originally created in China,its process must use heavy metal compounds.At present,research on preserved eggs is mainly about the optimization of pickling process.Studies have shown that heavy metal compounds can not only regulate the rate of alkali infiltration,but also can directly interact with proteins to affect the coagulation of preserved eggs.Therefore,the regulation mechanism of metal ions on egg white gel needs further elucidation..In addition,although metal elements such as copper and zinc are currently used instead of lead for processing preserved eggs,excessive intake of metal elements can be harmful to health.All in all,it is necessary to clarify the influence of other metal ions on egg white gels and find alternatives to heavy metal compounds.In this paper,the effects of three kind of metal liquid on the physicochemical properties,ultrastructure and digestive properties of preserved eggs were firstly studied.Binding alkalinity of material liquid and pH variation of the egg during processing,by optimizing the alkali concentration,temperature and time to establish outside shell egg white/ovalbumin gel model induced by strong alkali.At the same time,the establishment of a metal ion-egg white protein aggregates model induced by strong alkali,in order to investigate changes of the particle size and distribution of different metal salts-egg white aggregates?in vitro model?induced by strong alkali.The main results are as follows:1.The efffects of metal ions on the physicochemical properties,ultrastructure and digestive properties of preserved egg white during pickling were determined.Preservation of preserved eggs requires the addition of metal salts.The rate of alkali entering the egg and the moisture content in the eggs will be affected by the type of metal ions added.The moisture and alkali content of preserved eggs preserved with copper alone were the largest among the three treatment groups.According to the change trend of hardness and moisture content of preserved egg white,the hardness of preserved egg white depends on the water content of the protein.In addition,the addition of metal ion can affect the color of preserved egg white gels.ESEM observed that the three-dimensional network structure of copper-zinc preserved egg white was the most intensive and the gel digestibility was also the lowest.As the pickling time increases,a large number of ionic bonds were converted into disulfide bonds,in which the quality of preserved eggs was related to the high content of disulfide bonds in the gel.In conclusion,the different types of metal salts added during pickling can affect the density of the internal structure of the gel and the disulfide bond content,which will change the physical and chemical properties of the gel.2.Preliminary explorated the mechanism of metal compounds to regulate the alkaline induced egg white gelOutside shell egg white model was established.With different ionic strengths and ion types,transparent gels,opaque gels,or turbid gels can be obtained under strong alkali treatment.The calcium ions and iron ions increased the turbidity of the gel significantly,indicating that the internal aggregates formed larger particles.Monovalent potassium ions can promote the dissolution of proteins,and the formed gels have very good hardness and structure,the water retention in accordance with the trend of the solubility.However,at higher concentrations,divalent and trivalent metal ions have inhibitory effect on the formation of the gel,which is not conducive to the formation of gel structure,and its water holding capacity is also significantly lower than that of potassium ion gel.The intramolecular forces of different kinds of metal ion gels are different from each other,indicating that different metal ions and proteins depend on different chemical forces.3.The effects of several commonly used heavy metal compounds on the gel properties of alkali-induced ovalbumin were clarifiedThe effect of different KCl?monovalent salts?,CaCl2,ZnCl2,CuSO4,CuCl2?divalent salts?,FeCl₃?trivalent salts?,and SO4^2-,Cl^-?anions?on strong alkali-induced ovalbumin gel properties was studied?in vitro model?.Zinc chloride,calcium chloride and ferric chloride both had significant effects on the particle size and shape of ovalbumin aggregates.The zinc chloride added ovalbumin paticles was significantly smaller than other gels.Combining the changes in molecular forces,it can be seen that calcium chloride,zinc chloride,and ferric chloride can influence the internal force of the support gel structure,as well as the size and shape of aggregates filled in the gel ultimately affect the formation of ovalbumin gel properties.By scanning electron microscopy?SEM?and transmission electron microscopy?TEM?were confirmed a ovalbumin gel added metal ions containing two components,one component is gel three-dimensional framework,the other is a type of metal ions-protein aggregates filled in a three-dimensional ovalbumin network structure.Metal ions can also influence the formation of ovalbumin gel by affecting the secondary structure of ovalbumin.