Preparation And Characterization Of Sodium Alginate-based Composite Film And Study On Storage Of Heavy Metals-free Preserved Eggs

Preserved egg is one of the unique traditional foods in our country,which are deeply loved by consumers.However,the quality of preserved eggs was reduced due to the influence of the environment during the storage process.The heavy metals-free preserved eggs that we have developed are especially difficult to store because they will shrink and fade during storage at room temperature.Therefore,this paper focused on heavy metals-free preserved eggs,and the effects of five different packaging methods on the quality of heavy metals-free preserved eggs during storage were explored.At the same time,the performance differences between different coating materials based on sodium alginate and gelatin were studied.And these were applied to the preservation of preserved eggs,and the influence of different coating liquids on the quality of preserved eggs was investigated,thereby providing a theoretical basis for the storage of heavy metals-free preserved eggs.1.The effect of five preservation methods including no packaging at room temperature(25℃),no packaging at low temperatures(4℃),wrapped in plastic bag,paraffin coating and vacuum packaging on the quality of heavy metals-free preserved eggs during the storage period was systematically studied.The results showed that the moisture content and pH value of preserved egg albumen stored under the five preservation methods continued to decrease,the mass loss rate continued to increase,the content of volatile base nitrogen increased first and then decreased,the hardness and springiness of preserved egg albumen continued to increase,and no microorganisms were affected.Among them,the water retention and quality loss prevention performance of preserved egg albumen packaged with paraffin was the best,and it only decreased by 0.34% and 1.24% after three months.The vacuum-packed preserved eggs had the best elasticity after three months of storage,the color changed to dark brown,and the sensory score was the highest at 70.5 points.It can be concluded that the preservation effect of paraffin coating and vacuum packaging was better.2.The effect of different concentrations(1%,3% and 5%)of bacterial cellulose addition on the properties of sodium alginate and sodium alginate gelatin film was explored.The results showed that sodium alginate,gelatin and bacterial cellulose have good compatibility.Bacterial cellulose can effectively enhanced the mechanical properties of sodium alginate,and the tensile strength reached the maximum when the amount of bacterial cellulose added was 3%.At the same time,the water vapor permeability and moisture content of the film were significantly reduced,and the transparency of the film was improved.For the sodium alginate gelatin film,the tensile strength of the film was the largest when the bacterial cellulose content was 1%.The mechanical properties began to decline when the bacterial cellulose concentrations exceed 1%.However,the water vapor permeability and moisture content did not change much,and the opacity of the film increased.These showed that bacterial cellulose can effectively improve the functional properties of the film3.The pure sodium alginate coating solution,sodium alginate-gelatin coating solution and sodium alginate-gelatin-bacterial cellulose coating solution were respectively used in the preservation of heavy metals-free preserved eggs to explore their effects on the storage quality of heavy metals-free preserved eggs.The research results showed that the coating solutions of sodium alginate-gelatin and sodium alginate-gelatin-bacterial cellulose have better preservation effects on preserved eggs than pure sodium alginate coating solutions.They effectively slowed down the quality loss of preserved eggs and the loss of moisture in the albumen,and delayed the decrease of pH and the production of volatile substances.Among them,the preserved eggs of the sodium alginate-gelatin group had the lowest hardness and the lowest quality loss rate after three months of storage,and the preserved eggs coated with sodium alginate-gelatin-bacterial cellulose solution had the best effect on maintaining the unique color of preserved eggs.