Rheological characterization of rhea (Rhea americana) eggs subjected to different storage periods

Abstract Eggs are used as food industry ingredients due to their functional properties. Eggs from different bird species are used in industrial processing; therefore, rheological experiments were carried out at steady state to obtain the flow curves and also at a dynamic state to study the rheological properties of greater rhea eggs. The viscoelastic behavior of the fluids as a function of the coagulation temperatures for albumen and yolk and of the oscillatory shear frequency was studied. Fifteen rhea eggs stored for up to 28 days at 10 °C were analyzed at 1, 7, 14, 21, and 28 days. The albumen and yolk fractions showed pseudoplastic rheological behavior with small initial flow shear and dependence on shear time, with albumen demonstrating thixotropy and the yolk showing rheopexy. In low shear rheological tests, thermal gelation of albumen was observed, presenting a first change in the elastic modulus around 56 °C, and a second from 78 °C. In the yolk, a change was observed from 66 °C, with more structural variations in the development of the gel at higher temperatures. For rhea eggs, the gel structuring (gelation) temperature of albumen (80 °C) and egg yolk (69 °C) did not undergo variations during the storage periods. Compared to commercial eggs, the higher viscosity and gelation temperatures presented by the rhea eggs can help determine the size of the industrial processing system as they can be submitted to higher temperatures without modifying protein structures and hindering the process.

摘要 鸡蛋因其功能特性而被用作食品工业原料。不同鸟类的禽蛋均应用于食品工业加工流程中，为此本研究针对大美洲鸵蛋（greater rhea eggs）分别开展稳态流变实验以获取流动曲线，并通过动态流变实验探究其流变特性。本研究分析了蛋清（albumen）与蛋黄（yolk）的黏弹行为随凝固温度及振荡剪切频率的变化规律。本研究选取15枚在10℃环境下储存最长达28天的大美洲鸵蛋，分别在储存第1、7、14、21及28天开展检测分析。结果显示，蛋清与蛋黄组分均表现出假塑性流变行为，初始流动剪切应力较低且受剪切时间影响显著；其中蛋清呈现触变性，而蛋黄则表现出震凝性。在低剪切流变实验中可观测到蛋清的热胶凝过程：其弹性模量先在约56℃时发生首次突变，随后在78℃时出现第二次变化。对于蛋黄而言，其流变特性在66℃时出现明显变化，且在更高温度下胶凝过程中的结构演变更为复杂。针对大美洲鸵蛋的研究表明，蛋清（80℃）与蛋黄（69℃）的胶凝形成温度在整个储存周期内均未发生显著波动。与市售商品鸡蛋相比，大美洲鸵蛋具备更高的黏度与胶凝温度，这一特性可辅助确定食品工业加工系统的规模——因其可在更高温度下进行处理而不会改变蛋白质结构、阻碍加工进程。