# The Quality Analysis and Deterioration Mechanism of Liquid Egg White during Storage
## 3 Results and Discussion
### High-Throughput Sequencing Analysis
#### 3.3.3 Bacterial Abundance and Distribution  
As shown in Figure 4c,d, the 4 \({}^{\circ}\)C and 10 \({}^{\circ}\)C samples covered 17 and 18 families at the family level, respectively, showing similarity in the invasion species in both groups during the process of egg white spoilage. The dominant bacteria in the 4 \({}^{\circ}\)C group were from others (32.27%), _Enterobacteriaceae_ (30.70%), and _Bifidobacteriaceae_ (18.78%). The bacteria in the 10 \({}^{\circ}\)C group with the highest abundance belonged to _Pseudomonasaceae_ (21.8%), followed by _Moraxellaceae_ (14.35%), others (13.62%), and _Enterobacteriaceae_ (12.3%). These results suggested that the dominant spoilage bacteria were markedly different in the two groups, which might be attributed to the different optimum growth temperatures of spoilage bacteria.  
Figure 4: (**a**) Dilution curve; (**b**) rank-abundance curve. Relative abundances of bacterial communities of LEW under (**c**) 4 \({}^{\circ}\)C and (**d**) 10 \({}^{\circ}\)C storage conditions at the family level.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **Ace** & **Chao** & **Coverage** & **Shannon** & **Simpson** \\ \hline
4 \({}^{\circ}\)C & 310 & 310 & 1.0 & 3.48 & 0.08 \\
10 \({}^{\circ}\)C & 761.2 & 761 & 0.99 & 4.01 & 0.13 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Diversity index.  
ria [49]. It has been reported that _Pseudomonadaceae_ often exists in the spoilage of cryogenic liquid eggs [50], which is consistent with the results of these experiments. _Pseudomonadaceae_ infection during breeding of poultry might occur through wounds, umbilical cords, environment, or infiltration through eggshells, and was also common in fresh eggs [51].  
As shown in Figure 5, _Pseudomonas_ (21.79%), others (19.21%), and _Escherichia_ (11.21%) were highly abundant in the 10 \({}^{\circ}\)C samples. The dominant bacteria in the 4 \({}^{\circ}\)C group were others (37.5%), _Escherichia_ (30.40%), and _Bifidobacterium_ (17.72%). Among the dominant bacteria in the 10 \({}^{\circ}\)C group, _Pseudomonas_, which is known to play an important role in egg spoilage [50], accounted for the largest proportion. As a saprophytic bacterium, _Pseudomonas_ are able to utilize new nutrients (lactate, succinate) after glucose depletion, giving them an ecological advantage over non-proteolytic bacteria or less-proteolytic bacteria [52]. The relative abundance of _Bifidobacterium_ in the 4 \({}^{\circ}\)C sample (17.72%) was higher than that in the 10 \({}^{\circ}\)C sample (7.10%). It has been reported that _Bifidobacterium_ has an antagonistic effect on the growth and reproduction of other bacteria [53], which may contribute relatively to extending the shelf life of LEW under a storage temperature of 4 \({}^{\circ}\)C. It is accepted that _Escherichia_ is an important contributor to the spoilage of eggs and egg-derived products [54]. In the present study, _Escherichia_ appeared at a relatively high abundance in the two groups, though especially in the 4 \({}^{\circ}\)C sample.  
The relative abundance and distribution of the microbial species showed significant differences in the two groups, which may be attributed to the following reasons. In the early stage of storage, different storage temperatures may be the main cause for the difference in microbial distribution between the two groups. Subsequently, depletion of glucose resources results in a shift from sacchaolytic to amino-acid degrading metabolism [52], leading to changes in bacterial species. Additionally, dominant bacteria controlled the population behavior by secreting soluble small molecules and gained survival advantages, which are called microbial quorum sensing [55]. Several studies have shown that _Enterobacteriaceae_ produce a rich array of molecules that might affect bacterial traits, which were involved in the process of product spoilage during storage [56; 57].  
Figure 5: Relative abundances of bacterial communities of LEW at the genus level.