How does soy 7S globulin influence the thermo-responsive fibration process of methylcellulose chains in aqueous solutions?

Abstract

In the past decade, there is a number of studies focusing on the interactions between methylcellulose and ions/surfactants, whereas in real food and material systems, methylcellulose is widely co-existing with natural macromolecules such as polysaccharides and proteins, but their interplay has been scarcely studied so far. In this work, by selecting soy 7S globulin as a model protein, we have investigated the interplay between methylcellulose and soy 7S globulin in aqueous solutions, and its influence on the thermo-responsive behavior of methylcellulose chains. By combining particle sizing, isothermal titration calorimetry and cloud point measurements, it is observed that the addition of 7S globulin induces the formation of 7S globulin-methylcellulose aggregates, mainly driven by the weak hydrophobic force (∼ 0.03 kJ/mol) at T = 25 °C, and facilitated the formation of 7S globulin-methylcellulose fibrils aggregates at T = 50 – 70 °C, which shows thermo-responsive behavior. Atomic force microscopy and rheology results signify that the 7S globulin probably acted as multi-site centers to bridge fibrils together and eventually formed large spherical aggregates covered with reticular fibrous structures, along with the decrease in the modulus of 7S globulin-methylcellulose gel network, which is due to the heterogeneous distribution of aggregates and poor continuity of network. This study not only reveals the influence of 7S globulin on the thermo-responsive behavior of methylcellulose but also lays a foundation for further optimizing the performance of the 7S globulin-methylcellulose system in real food and material systems.