## 4 Discussion
These changes can also be explained by variations in protein structure: alterations in the secondary structure of proteins exposed the hydrophobic bonds, and as such, led to formation of loose structures, which increased the water holding capacity [44]. Moreover, it could be inferred that variations in compactness and moisture traits based on sensory evaluation could be attributed to the differences in textural properties, i.e., hardness, springiness, gumminess, and chewiness, as well as the composition and structure of yolk lipids. The overall flavor characteristics may be determined, to an extent, by aroma and flavor attributes, which must be appealing to the consumers for acceptability. In this study, the egg yolk flavor of the Xinyang Blue and Xueyu White had stronger milky flavor, compared to that of Hy-Line Brown. However, the salty flavor of egg yolk from Xueyu White was more obvious, compared to that of other breeds. The variation in the milky flavor of egg yolks may be due to fatty acid content. There is evidence in the literature that the milky flavor of egg yolk may be influenced by fatty acid content in the egg yolk. Reports demonstrated the enhancement of milky flavor of egg yolk, due to the decomposition of stearic acid, oleic acid, and linolenic acid, due to heat treatment [45], increased the content of oleic acid in the egg yolk, due to dietary effect of hempseed and hempseed oil [46], and increased content of oleic acid and arachidonic acid [37]. In this study, the higher milky flavor score of egg yolk from Xinyang Blue and Xueyu White breeds may be explained by the variation in the egg yolk content of oleic acid and arachidonic acid. Salty flavor is generally the taste of a salt solution. The salty flavor score of the egg yolk was positively correlated with the response value of the E-tongue umami sensor and was negatively correlated with the n-3 PUFA content. Recent research had shown that saltiness perception was affected by the increase in umami sensors [47]. Therefore, the significant salty flavor scores of egg yolk from Xueyu White could be linked to alterations in n-3 PUFA content and sensitivity of the umami sensors. Invariably, the umami sensors may be influenced by the composition and content of amino acids and lipids, which was the characteristic flavor of egg yolk [48]. Additionally, umami sensory scores were regulated by arachidonicic acid, due to its influence on cation channels [49], while the umami flavor could be affected by the composition and content of amino acids and 5'- nucleotides [38]. Furthermore, the E-tongue umami sensor mainly uses the electrostatic interaction between the lipid film and the odorant to generate potential changes and output them as visual data [19]. Instrumental detection and sensory evaluation had different perceptions of umami in the current study in same lieu, and the study of [PERSON] et al. [27] showed that sensory evaluation could not distinguish the flavor difference of eggs produced by adding yeast biomass in feed, but the instrument could distinguish the flavor and aroma of eggs. Taken together, the salty flavor score of egg yolk was positively correlated with the response value of the E-tongue umami sensor and may be related to the content of arachidonic acid. The breed differences for milky flavor are explained by the variation in the egg yolk content of fatty acids (oleic acid and arachidonic acid) among the breeds. In order to further establish the components and characteristic that contributed to the egg yolk flavor, we determined the aroma, flavor characteristics, and volatile compounds that may contribute to egg yolk flavor using sensory evaluation and instrument detection. Compared with the Xinyang Blue, the aroma preference score of Hy-Line Brown and Xueyu White was higher, and the score of egg aroma increased, but the difference was not significant.