Eggs Microbiological Testing And Research On The Relationship Between Egg Quality And Impedance Under Different Conditions

Eggs are an important compnent of people's daily life because of the rich nutrients and the cheap price.Eggs risk microbial contamination in the process of production,transportation and storage,microbial contamination will not only make the eggs lose their edible value,resulting in huge economic losses,but also lead to more serious food safety problems.In this study,the aerobic plate count,the microbial species,the bacterial community relations,the impedance and the egg quality of the eggs in different conditions were studied.The main contents of this study included three parts.The first part: Fresh eggs were obtained from the Jiufeng Xinyue farm,and the eggs were subsequently stored at room temperature nearly 25 ? and low temperature at 4 ?.The clone total number of eggshell,egg white,yolk changes and egg white changes in impedance were determined,at the same time,microorganisms of the egg white and yolk were isolation and identification.The result indicated that the initial aerobic plate count was 2.77 log CFU/eggshell and the aerobic plate count of the eggshell increases with the storage time,the aerobic plate count on the eggshell on the range of 2.77-4.39.Egg yolk and egg white were not to be detected in the presence of microorganisms at the beginning,it is until 20 d to detect the presence of microorganisms,the aerobic plate count of the egg yolk,egg white increased with storage time.A total of 86 kinds of bacteria were isolated from the surface of the egg during the storage at 25 ?,25 kinds of bacteria were isolated from the egg white,and18 kinds of bacteria were isolated from the egg white.The logarithm of the initial colony count of the shell was 3.6 when storage at 4 ?,and the aerobic plate count of eggshell showed a trend of increasing and then decreasing,but increasing after decreasing.The reason of the decrease was due to the low temperature or the fewer nutrients.There are 74 kinds of bacteria isolated from the eggshell in the process of storage at 4 ?,but few bacteria isolated from egg content.Therefore,the low temperature storage conditions can effectively delay the microbial invasion into eggs and extend the shelf life of eggs.The second part: using metagenomic sequencing to investigate the microorganism on the eggshell,and the result showed that the number of OTU of sample A and sample B was 7828,of which the number of OTU of sample A was5093 and the number of OTU of sample B was 4524,which indicating that the bacterial on eggshell is very rich.Through the analysis of Alpha diversity of egg samples,it was found that the bacterial community diversity was high.Result of bacterial community on Eggshell showed that the number of Proteobacteria and Firmicutes on the eggshell is the most high,and sample A and sample B has the same bacterial community composition at the genus level,but the number of different bacteria is different.The third part: There were 9 different experimental conditions after combination of three kinds of temperature(4 ?,25 ?,37 ?)and three types of humidity(RH75%,RH75%,RH5%),and egg's haugh unit,yolk index,p H and impedance were detected during storage time.The results showed that the haugh unit,yolk index and impedance decreased with storage time,and p H increased with storage time.The quality of eggs varied under different storage conditions.The lower the temperature and the smaller the humidity,the better the quality of eggs,so the eggs shelf life can be properly extended when placed at low temperature and in dry environment.Impedance of the eggs during different storage conditions showed good correlation with egg quality(haugh unit,yolk index,p H),so impedance can represent egg quality under certain conditions.