不同碱处理对蛋清凝胶物理化学变化的影响研究

Effect of Alkali Treatments on the Physicochemical Properties of Egg White Gels

采用两种碱处理加工方式制成蛋清凝胶制品(蛋清碱诱导凝胶和皮蛋清),以TPA(Texture Profile Analysis)、溶解度、巯基与二硫键含量、表面疏水性、蛋白质组分、微观结构、蛋白质二级结构为考察指标,研究蛋清碱诱导凝胶与皮蛋清凝胶特性的差异及其作用机理,结果表明:各碱处理组蛋清的蛋白质分子高度交联而形成凝胶网络结构,且蛋清碱诱导凝胶组较为致密有序。蛋清碱诱导凝胶比皮蛋清具有较高的硬度(186.73±3.29 g)、内聚性(0.98±0.02)、咀嚼性(176.21±6.13)、溶解度(55.68±1.20%)、表面巯基(60.34±1.01μmol/g)和二硫键含量(29.42±0.57μmol/g),且具有较低的总巯基含量(64.60±2.28μmol/g)和表面疏水性(419.80±17.22)。蛋清碱诱导凝胶蛋白质二级构象以β-折叠为主(31.24%),分子内具有较强的氢键总相互作用;皮蛋清蛋白质二级结构中α+β构象较低(33.65%),β1(21.21%)、T-转角(25.36%)和γ无规则卷曲(19.78%)较大。蛋清蛋白质组分在两种碱处理加工方式下都发生明显变性。

Difference of gel properties and the mechanisms between alkali-induced egg white gel and lime-preserved egg white were investigated by studying the variations of texture profile analysis （TPA）, solubility, sulphydryl content, disulfide bond content, surface hydrophobicity, protein fractions, microstructure and protein secondary structure of egg white gels obtained from different alkali treatments. The results showed that protein molecules of egg white obtained from both alkali treatments formed highly cross-linked gel network structures, and closer and more orderly protein aggregates with denser network were observed in alkali-induced egg white gel. The hardness （186.73±3.29 g）, cohesiveness （0.98±0.02）, chewiness （176.21±6.13）, solubility （55.68±1.20%）, exposed sulphydryl content （60.34±1.01 μmol/g） and disulfide bond content （29.42±0.57 μmol/g） of alkali-induced egg white gel were higher than that of lime-preserved egg white, while total sulphydryl content （64.60±2.28 μmol/g） and surface hydrophobicity （419.80±17.22） were lower. Protein secondary structure of alkali-induced egg white gel was mainly in β-sheet （31.24%）, which showed the strong total hydrogen bonding interaction in the molecules. And the content of α＋β conformation （33.65%） was lower in protein secondary structure for the lime-preserved egg white, but contents of β1 （21.21%）, T-turn （25.36%0） and 7-random （19.78%） coil were higher. Therefore, egg white proteins denatured obviously by the two alkali treatments.