## 4 Discussion  
The Xueyu White and Xinyang Blue are Chinese indigenous breeds and are local-ly reared, while the Hy-Line Brown is used for commercial purposes. The assessment of egg yolk flavor preference based on sensory evaluation indicated that there were significant differences in flavor preference, texture preference, and overall preference. Furthermore, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Items** & **Hy-Line 1** & **Xueyu 1** & **Xinyang 1** & **SEM 2** & _p-Value_ \\ \hline Cohesiveness & 0.43 & 0.45 & 0.40 & 0.02 & 0.50 \\ Springiness (mm) & 5.20 b & 5.70 a & 3.80 c & 0.16 & \textless{}0.01 \\ Gumminess (N) & 1.83 ab & 2.07 a & 1.31 b & 0.12 & 0.03 \\ Chewiness & 7.76 a & 8.03 a & 4.53 b & 0.45 & \textless{}0.01 \\ Hardness (N) & 3.87 b & 4.80 a & 3.27 c & 0.17 & \textless{}0.01 \\ \hline \hline \end{tabular}  
* \({}^{\text{1}}\)Hy-Line, Hy-Line Brown. Xueyu, Xueyu White. Xinyang Blue, the below is the same. 2 SEM, standard error of the mean, the below is the same. a–c Means within a row with no common superscripts differ significantly (\(p<0.05\)), and below is the same.  
\end{table} 
Table 6: Texture of egg yolks from Hy-Line, Xueyu, and Xinyang laying hens. Figure 5: An overview of the correlation loadings from PLS analyses with texture as X-variables and sensory attributes as Y-variables. Note: Hy-Line: Hy-Line Brown; Xueyu: Xueyu White; Xinyang: Xinyang Blue. previous studies mostly focused on evaluation of egg aroma, flavor, texture, and overall preference on a singly basis [27; 37; 40]. In the present study, all the variables were examined together to provide a basis for results validation. The overall preference for egg yolk flavor was highly positively correlated with texture, flavor, and aroma preference. This suggests that breed differences contributed to variation in the results of egg yolk flavor preference, while texture and flavor were the main factors affecting preference for egg yolk flavor. The egg yolk compactness and moisture scores of Xinyang Blue and Xueyu White were better than that of Hy-Line Brown. The changes in the texture of egg yolk from various breeds might be a function of molecular and structural changes in the yolk components in response to heat (boiling). Heating influences the distribution of egg yolk lipids, which is often influenced by egg weight, but egg weight was not significantly different in this study. Therefore, there may be another rationale to explain the changes in egg yolk texture. Egg yolk consists mainly of lipoprotein molecules (combined with protein and lipid); therefore, lipoprotein composition and structure exert significant influence on yolk texture [41]. Additionally, the lipid oxidation of egg yolk results in the dissolution of lipids, and that enhances the springiness of egg yolk texture [42]. During the heating process, lipids migration occurred in steamed eggs to form high-fat and low-fat structures, respectively. In the high-fat structure, the protein molecules are unfolded, and the crystallization rate becomes low, thus stabilizing the egg yolk texture, while increasing the hardness [31]. It has been reported that the addition of oil to egg yolk causes a change in the egg yolk lipoprotein structure and texture [42]. Further on, moist relates to the moisture content in the egg yolk, and moisture was positively correlated with textural hardness and cohesiveness in this study. Prior to boiling of the egg yolk samples, we tested the water content of the raw egg yolk (51.73 \(\pm\) 2.08), and there were no significant variations among the egg yolk samples for water content. Therefore, the positive correlation between egg yolk moisture and egg yolk cohesiveness was not due to water content. Additionally, the size of surface pores of boiled egg yolk particles images viewed under scanning electron microscopy were large, due to increased cohesiveness, as a result of water evaporation during heating [43].