目的:油菜籽中存在两个主要的蛋白质家族,即十字花科和纳丁斯。两种蛋白质家族之间的结构差异表明,当它们的混合物稳定油水界面时,它们的行为可能有所不同。因此,这项工作的重点是阐明蛋白质在界面和乳液稳定中的作用。
方法:评估蛋白质分子特性,使用SEC,DSC,CD,和疏水性分析。使用LAOS和LAOD研究了油水界面的力学性能。一般应力分解(GSD)被用作表征非线性响应的新方法。此外,为了评估菜籽蛋白的乳化特性,乳液是使用纯napins或十字花素及其混合物以1:3、1:1和3:1(w:w)的比例制备的。
结果:十字花胶形成坚硬的粘弹性固体状界面层(Gs'=0.046mN/m;Ed'=30.1mN/m),而napin在油水界面形成较弱和更可拉伸的层(Gs'=0.010mN/m;Ed'=26.4mN/m)。因此,十字花科蛋白形成的油滴具有更高的抗聚结稳定性(聚结指数,在两个月的储存期间,CI高达10%)比napin稳定的CI(CI高达146%)。两种蛋白质在用凝固素-十字花素混合物生产的乳液中具有不同的作用,十字花科提供高聚结稳定性,而napin诱导絮凝。我们的工作显示了每种菜籽蛋白在液-液多相系统中的作用。
OBJECTIVE: Two major protein families are present in rapeseed, namely cruciferins and napins. The structural differences between the two protein families indicate that they might behave differently when their mixture stabilises oil-water interfaces. Therefore, this work focuses on elucidating the role of both proteins in interface and emulsion stabilisation.
METHODS: Protein molecular properties were evaluated, using SEC, DSC, CD, and hydrophobicity analysis. The oil-water interface mechanical properties were studied using LAOS and LAOD. General stress decomposition (GSD) was used as a novel method to characterise the nonlinear response. Additionally, to evaluate the emulsifying properties of the rapeseed proteins, emulsions were prepared using pure napins or cruciferin and also their mixtures at 1:3, 1:1 and 3:1 (w:w) ratios.
RESULTS: Cruciferins formed stiff viscoelastic solid-like interfacial layers (Gs\' = 0.046 mN/m; Ed\' = 30.1 mN/m), while napin formed weaker and more stretchable layers at the oil-water interface (Gs\' = 0.010 mN/m; Ed\' = 26.4 mN/m). As a result, cruciferin-formed oil droplets with much higher stability against coalescence (coalescence index, CI up to 10%) than napin-stabilised ones (CI up to 146%) during two months of storage. Both proteins have a different role in emulsions produced with napin-cruciferin mixtures, where cruciferin provides high coalescence stability, while napin induces flocculation. Our work showed the role of each rapeseed protein in liquid-liquid multiphase systems.