Glyn O. Phillips Hydrocolloid Research Centre, National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Department of Bioengineering and Food Science, Hubei University of Technology, Wuhan 430068, China.
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.
Soft Matter. 2021 Mar 18;17(10):2973-2984. doi: 10.1039/d0sm01761b.
During processing, proteins are easily self-assembled into different aggregates, such as nanoparticles and fibrils. Protein aggregates exhibit a strong interfacial activity due to their morphologies and functional groups on the surface. Their interfacial structure and rheological properties at the oil-water interface have a significant effect on the stability and fat digestion of emulsions in food. In this study, β-lactoglobulin (β-lg) aggregates including β-lg nanoparticles (β-lg NP) and β-lg fibrils (β-lg F) were prepared in solution by controlling the heating temperature and pH, and their surface properties including the electric potential, hydrophobicity, and density of free thiol groups were characterized. The adsorption kinetics, interfacial rheology, and displacement by bile salts (BSs) of native β-lg and its aggregates at the oil (decane)/water interfaces were studied using particle tracking microrheology and dilatational rheology. From the movement of tracer particles at the interface, β-lg NP and β-lg F were found to adsorb faster than native β-lg, and they were found to form interfacial films with a marginally higher elasticity. During the process of protein adsorption, the films of β-lg and its aggregates are not uniform. In the process of protein displacement, β-lg NP has the strongest ability while native β-lg has the weakest ability to resist BS substitution, which is consistent with the results from in vitro digestion experiments. The present study reveals the microrheological behaviour of protein aggregates at the oil-water interface and demonstrates that β-lg thermal aggregates exhibit an excellent emulsification ability and can be used to control fat digestion. The study also illustrates the applicability of microrheological methods to the study of interfacial rheology and its complementarity with dilatational rheological methods.
在加工过程中，蛋白质很容易自组装成不同的聚集体，如纳米颗粒和纤维。由于其形态和表面官能团，蛋白质聚集体表现出很强的界面活性。它们在油水界面的界面结构和流变性质对食品乳液的稳定性和脂肪消化有重要影响。在本研究中，通过控制加热温度和 pH 值，在溶液中制备了包括β-乳球蛋白纳米颗粒（β-lg NP）和β-乳球蛋白纤维（β-lg F）在内的β-乳球蛋白（β-lg）聚集体，并对其表面性质，包括电动电位、疏水性和自由巯基密度进行了表征。利用粒子跟踪微流变学和扩张流变学研究了天然β-lg及其聚集体在油（癸烷）/水界面上的吸附动力学、界面流变学和胆汁盐（BS）置换。从界面上示踪粒子的运动可以发现，β-lg NP 和β-lg F 的吸附速度比天然β-lg 快，并且它们形成的界面膜弹性略高。在蛋白质吸附过程中，β-lg 和其聚集体的膜并不均匀。在蛋白质置换过程中，β-lg NP 的能力最强，而天然β-lg 的能力最弱，无法抵抗 BS 取代，这与体外消化实验的结果一致。本研究揭示了蛋白质聚集体在油水界面上的微流变行为，并证明了β-lg 热聚集体具有优异的乳化能力，可用于控制脂肪消化。该研究还说明了微流变学方法在界面流变学研究中的适用性及其与扩张流变学方法的互补性。
