There are increasing interests in developing food-grade colloidal particles as effective Pickering stabilizers for oil-in-water (o/w) emulsions, due to their good potential to elaborate novel functional foods. Many globular food proteins have been well recognized to be a kind of effective emulsifying agents, but their Pickering-like stabilization as in particle-stabilized emulsions is very rarely reported. Soy proteins, one of the most important vegetable proteins, are easily denatured and thus usually present in the aggregated form. Soy glycinin (11S globulins) is the component in soy protein isolate exhibiting the highest tendency of insoluble nature, suggesting that soy proteins and soy glycinin in particle would be an excellent protein sources to be developed into effective Pickering stabilizers. In the present work, the potential of soy glycinin as a kind of Pickering-like stabilizers to stabilize o/w emulsions was investigated. Interestingly, we showed that native soy glycinin molecules were a kind of spherical nanoparticles with hydrodynamic radius (Rh) of approximately 30 nm, and a thermal pretreatment (at temperatures of 80-100°C) resulted in a significant increase in Rh, with the Rh increasing from 35-40 to 75 nm as the temperature was increased from 80 to 100°C. The pretreatment also led to significant increases in surface hydrophobicity. However, even after the heating at 100°C, the protein dispersions were basically kept transparent, confirming the formation of nanoparticles. All the emulsions formed at varying concentrations (c; 0.5-4.0%) exhibited a similar creaming behavior, but the droplet size progressively decreased with increasing the c, or the temperature of the pretreatment. All the formed emulsions were very stable against coalescence, even after storage up to 4 weeks. If the oil fraction was increased above 0.7 (at c =4%), the formed emulsions would exhibit a gel-like behavior. The results confirm that soy glycinin nanoparticles can be applied as an effective Pickering-like stabilizers, and the size and surface hydrophobicity of these nanoparticles could be modulated by a heat pretreatment with varying temperatures.
Principal investigator: Prof. Chuan-He Tang chtang@scut.edu.cn
