Effects Of Temperature And Gelatin-based Composite Coatings On The Quality Of Preserved Eggs During Storage

Preserved eggs are the original traditional egg products of our country,different storage temperatures and packaging methods will eventually lead to different degrees of changes in the quality of preserved eggs.This thesis takes preserved eggs as the research object,compares the quality changes of preserved eggs stored at different temperatures(4,25,35?),and develops green coating materials mainly based on gelatin and bacterial cellulose.Preservation of preserved eggs with coatings,observation of the effects of different coating on storage of preserved eggs,and providing a theoretical basis for storage quality control of preserved eggs:1.The effects of three different storage temperature(4,25,35?)on sensory quality,physicochemical properties,texture,molecular forces,flavor and microbial indexes of preserved eggs were studied.The results showed that the sensory quality,.weight loss rate,pH and color of preserved eggs were significantly different at different storage temperatures(p<0.05).Within 12 weeks of storage,Compared with high temperature and normal temperature storage,low temperature storage reduced weight loss rate by 55.15%and 64.1%,respectively,improved the sensory score(p<0.05),inhibited the reduction of pH and the increase of total volatile base nitrogen(p<0.05),and decreased the change of color(p<0.05).During storage,there was no different in the springiness of preserved egg white stored at different temperatures(p>0.05).Hardness and chewiness of three temperatures increased first and then decreased,and low temperature significantly inhibited the progress of these changes to a certain extent(p<0.05).The content of ionic bond in egg white first decreased and then increased,and content of disulfide bond increased first and then decreased.Content of ionic bond in yolk decreased all the time,and high temperature could promote this change.Whatever the temperature was,the content of free amino acids in preserved egg white and yolk increased first and then decreased,and the total content of amino acids stored at different temperatures was significantly different(p<0.05).The content of free fatty acids in yolk decreased.At the end of storage,no microorganisms were detected in three temperature during the storage period of 84 days.The results showed that low temperature storage is more conducive to preservation of preserved eggs.2.Four kinds of coating materials mainly made of gelatin and bacterial cellulose were developed,and the properties of the coating materials were characterized.The experimental results show that the film forming ability of the four coatings are all good.Bacterial cellulose reduces the viscosity,storage modulus and loss modulus of gelatin films.Microstructural observations show that compared to a single gelatin film,the addition of bacterial cellulose makes the structure of the composite film more compact and complete.At the same time,the addition of bacterial cellulose will change the gelatin fi.lm material from hydrophilic to hydrophobic.Bacterial cellulose and nano-compounds can reduce the moisture permeability of gelatin film,which can significantly reduce the water vapor transmission rate(p<0.05).After blending,the tensile strength and elastic modulus of the composite film are reduced,the tensile fracture rate is increased,the brittleness of the film is reduced,and the toughness is increased.DSC results show that the addition of bacterial cellulose will reduce the glass transition temperature and increase the enthalpy change of the composite membrane,and the nano compounds have a significant effect on the enthalpy change of the composite membrane(p<0.05).3.The prepared four coating materials were used to coat the preserved eggs,and then storage experiments were performed to observe the changes in the quality of the preserved eggs.The results show that the coating material can reduce the entry of oxygen,thereby reducing the oxidation of fatty acids or other substances,and reducing the rate of generation of basic nitrogen-containing substances,delaying the decline in pH,and thus delaying the rise of volatile basic nitrogen;On the one hand,the loss of water dispersion is reduced,thereby inhibiting the shrinkage and hardening of the preserved egg protein.During the storage process,the sensory quality and pH values of the preserved eggs decreased more slowly than those of the control group.The mass loss rate,hardness,chewability,and volatile base nitrogen all increased more slowly than the control group,and the differences were significant(p<0.05),indicating that the preserved eggs were subjected to gelatin After the coating is applied,the quality can be better maintained.Compared with a single gelatin film,the gelatin composite film added with bacterial cellulose can significantly delay the increase of volatile base nitrogen(p<0.05),It is concluded that considering the cost of film production and the effect of preservation,group B coating materials are better.