Jiangxi Key Laboratory of Natural Products and Functional Food, Jiangxi Agricultural University, Nanchang 330045, China.
Engineering Research Center of Biomass Conversion, Ministry of Education, Nanchang University, Nanchang 330047, China.
Poult Sci. 2019 Oct 1;98(10):5166-5176. doi: 10.3382/ps/pez232.
Salted eggs, which are a traditional Chinese egg product, are favored by Chinese consumers and have become very popular in other Asian countries due to their unique features such as "fresh, fine, tender, loose, gritty and oily texture." In order to illuminate the forming process of salted egg, the gelation behavior and mechanism of low-density lipoprotein (LDL) induced by NaCl were investigated using marinated model outside the eggshell. Results showed that as the salting proceeded, the moisture content exhibited a decreasing trend. The NaCl content, oil exudation, hardness, and surface hydrophobicity showed constantly increasing trends. In the early stages of salting, the size of the LDL particles, soluble protein content, and T21 increased, whereas T21 (with D2O), T22, and the free sulfhydryl content declined. In the later stages of salting, LDL formed a multiple composite aggregate gel structure with filamentous apoproteins and non-spherical lipid particles intertwined with each other. The soluble protein content and T23 (without D2O) decreased, whereas T21 (with D2O), T22 and the free sulfhydryl content increased. Fourier transform infrared spectroscopy revealed that the fresh LDL mainly consisted of α-helix and β-sheet structures. After the gel becomes hardened, the LDL secondary structure was changed remarkably, characterized by the decrease of α-helix elements and increase of β-sheet elements. The results suggested that the oil exudation of salted LDL gels was mainly due to LDL destruction and the release of components (apoproteins, phospholipids, and neutral lipids) facilitated by increased interactions between apoproteins and lipids.
咸蛋是中国传统的蛋制品，由于其“鲜、细、嫩、松、沙、油”的独特风味而深受中国消费者的喜爱，并在其他亚洲国家迅速流行起来。为了阐明咸蛋的形成过程，采用蛋壳外腌制模型研究了 NaCl 诱导的低密度脂蛋白（LDL）的胶凝行为和机制。结果表明，随着腌制的进行，水分含量呈下降趋势；NaCl 含量、油渗出、硬度和表面疏水性呈不断增加的趋势。在腌制的早期阶段，LDL 颗粒的大小、可溶性蛋白含量和 T21 增加，而 T21（带 D2O）、T22 和游离巯基含量下降。在腌制的后期阶段，LDL 形成了具有丝状载脂蛋白和非球形脂质颗粒相互交织的多重复合聚集凝胶结构。可溶性蛋白含量和 T23（不带 D2O）下降，而 T21（带 D2O）、T22 和游离巯基含量增加。傅里叶变换红外光谱表明，新鲜 LDL 主要由α-螺旋和β-折叠结构组成。胶凝后，LDL 的二级结构发生了显著变化，特征是α-螺旋元素减少，β-折叠元素增加。结果表明，咸 LDL 凝胶的油渗出主要归因于 LDL 的破坏以及载脂蛋白和脂质之间相互作用的增加导致的成分（载脂蛋白、磷脂和中性脂质）的释放。
