Roullet Marion, Clegg Paul S, Frith William J
Unilever R&D Colworth, Sharnbrook, Bedford MK44 1LQ, UK; School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
J Colloid Interface Sci. 2020 Nov 1;579:878-887. doi: 10.1016/j.jcis.2020.05.004. Epub 2020 Jul 5.
Protein-stabilised emulsion gels can be studied in the theoretical framework of colloidal gels, because both protein assemblies and droplets may be considered as soft colloids. These particles differ in their nature, size and softness, and these differences may have an influence on the rheological properties of the gels they form.
Pure gels made of milk proteins (sodium caseinate), or of sub-micron protein-stabilised droplets, were prepared by slow acidification of suspensions at various concentrations. Their microstructure was characterised, their viscoelasticity, both in the linear and non-linear regime, and their frequency dependence were measured, and the behaviour of the two types of gels was compared.
Protein gels and droplet gels were found to have broadly similar microstructure and rheological properties when compared at fixed volume fraction, a parameter derived from the study of the viscosity of the suspensions formed by proteins and by droplets. The viscoelasticity displayed a power law behaviour in concentration, as did the storage modulus in frequency. Additionally, strain hardening was found to occur at low concentration. These behaviours differed slightly between protein gels and droplet gels, showing that some specific properties of the primary colloidal particles play a role in the development of the rheological properties of the gels.
蛋白质稳定的乳液凝胶可以在胶体凝胶的理论框架内进行研究，因为蛋白质聚集体和液滴都可被视为软胶体。这些颗粒在性质、大小和柔软度方面存在差异，而这些差异可能会对它们形成的凝胶的流变特性产生影响。
通过对不同浓度的悬浮液进行缓慢酸化，制备了由乳蛋白（酪蛋白酸钠）或亚微米级蛋白质稳定液滴制成的纯凝胶。对它们的微观结构进行了表征，测量了它们在线性和非线性区域的粘弹性及其频率依赖性，并比较了这两种类型凝胶的行为。
当在固定体积分数下进行比较时，发现蛋白质凝胶和液滴凝胶具有大致相似的微观结构和流变特性，固定体积分数是一个从对由蛋白质和液滴形成的悬浮液的粘度研究中得出的参数。粘弹性在浓度上呈现幂律行为，储能模量在频率上也是如此。此外，发现在低浓度下会发生应变硬化。蛋白质凝胶和液滴凝胶之间的这些行为略有不同，表明初级胶体颗粒的一些特定性质在凝胶流变特性的发展中起作用。
