The Quality And Deterioration Mechanism Of Egg White Liquid During Storage

Egg white liquid is a liquid egg product obtained by egg yolk separation,filtration and pasteurization after egg breaking.It has the advantages of rich nutrition,convenient storage and transportation,and high safety.In addition,it also has functional properties including gelling,foaming and emulsifying properties,and is widely used in meat products,surimi products and flour products.At present,tin plate,plastic and glass are the main packaging materials in the industrial production of egg white liquid are mainly.The packaging materials are important influencing factors for the deterioration of sensory quality,proliferation of spoilage microbial and the change of functional characteristics during storage and transportation of egg white liquid.Therefore,egg white liquid was taken as the research object in this study,and the effects of glass,plastic and port iron packaging materials on the quality of egg white liquid(sensory quality,physical and chemical quality,functional quality,and microbial index)were analyzed.The effects of temperature on egg white protein structure were preliminarily explained through particle size analysis,surface hydrophobicity,and free sulfhydryl content.The bacterial community diversity of egg white liquid at different storage temperatures was explored by high-throughput detection technology.It is hoped that this study could provide theoretical basis and technical support for the industrial production of egg white liquid.The main research contents and results were as follows:(1)According to results of the total number of colonies,the shelf life of egg white liquid packaged with glass,plastic and port iron was preliminarily determined to be 8,6 and 5 days,respectively,and the shelf life of egg white liquid packaged with glass was the longest.With the increase of storage time,the total sensory scores of egg white liquid of the three packaging materials showed a significant downward trend as a whole(p < 0.05),and the p H values reached the maximum values on the 8th,6th and 5th days,respectively(9.29,9.29,9.33).The L value of egg white fluid decreased significantly(p < 0.05)as a whole,the change trend of a value was opposite,and the change of b value fluctuated greatly.Combining with the change of L,a and b values,the color change of tin packaging egg white fluid packaged was the most obvious,and tin plate was not conducive to maintaining the color of egg white fluid.The TVB-N content of egg white liquid with different packaging materials showed a significant upward trend(p < 0.05).The overall foaming ability was decreased firstly and then increased,and the gel hardness significantly decreased(p < 0.05).Compared with the other two packaging materials,the gel hardness of plastic packaging egg white liquid decreased the fastest.Considering the gel property,plastic packaging was not conducive to the storage of egg white liquid at room temperature.Considering the cost of packaging materials and the quality change of egg white liquid,glass packaging was more suitable for the storage and transportation of egg white liquid at room temperature than plastic and tin.Compared with fresh egg white solution,the total sensory scores of egg white solution at 20 °C,10 °C and 4 °C decreased by 35.7 %,32.7 % and 25.7 %,respectively,during 24 day of storage.On the 24 th day,the p H value of egg white liquid increased by 0.34 %,9.15 % and 9.15 %,compared with fresh egg liquid at 20 °C,10°C and 4°C,respectively.When the storage temperature was 10°C and 4°C,the L value of the egg white liquid showed a downward trend,and the b value decreased.During the entire storage process at 20°C,the L,a,b values of the egg white liquid fluctuated greatly.respectively,and the trend of foam stability was more complicated.However,the emulsification activity and emulsification stability of the egg white liquid decreased slowly under the storage condition of 10?(p>0.05),and the gelatinity of the egg white liquid significantly decreased at 20?(p<0.05).Therefore,considering the physical and chemical quality,emulsification and gel properties of the egg white liquid,compared with 20°C and 10°C,4°C is more conducive for the storage of the egg white liquid.(2)With the increase of thermal treatment temperature,the particle size of egg white liquid showed a significant upward trend compared with that of untreated egg white liquid(p< 0.05).When the heating temperature was 60 °C,the particle size reached a larger value(358.67 nm).Compared with the blank group,the surface hydrophobicity of egg white liquid increased by 13.44 % and 22.12 % when the heat treatment was 30 °C and 40 °C.The free thiol content reached the maximum value(10.51 umol / m L)when the heating temperature was50 °C.With the increase of low temperature heat treatment time,the average particle size of egg white liquid increased significantly(p<0.05),and it increased by 26.58 % compared with the blank.The surface hydrophobicity of egg white liquid was increased firstly and then decreased,and it reached a maximum value of 662.0 when the heating time was 30 min.The trend of free thiol content in egg white solution was consistent with that of surface hydrophobicity,and the maximum value was 7.865 umol /m L when the heating time was 30 min.(3)According to the Alpha data,the abundance of bacterial community in spoiled egg white liquid under storage conditions of 10? was greater than that under 4?storage conditions,while the diversity of bacterial community showed the opposite trend.At the phylum level,Firmicutes(67.42%)and Proteobacteria(16.55%)accounted for a highest abundance value in the 10°C spoilage egg white liquid sample(T sample),and Proteobacteria(45.30%),Actinomycota(29.45%)had a higher abundance value in the 4? spoilage egg white samples(F sample).From thelevel of the genus,the dominant spoilage bacteria in the F sample were Escherichia(30.40%)and Bifidobacterium(18.78%).Escherichia(11.21%),Pseudomonas(21.79%),and Bifidobacterium(7.10%)were the predominant spoilage genus in T samples.At the same time,there were also other groups with lower relative abundance that may affect the quality of egg white liquid,such as Ralstonia,Carnosus and other unknown groups.The above results indicated that temperature was an important factor affecting the diversity of the bacterial colony of spoilage in egg white liquid.