The effect of trehalose on the thermodynamic stability and emulsification of soybean 11S globulin in the molten globule state

Abstract

The molten globule (MG) state of soybean glycinin (11S) is partially folded at pH 1.0, so various polyhydroxyl osmotic agents are often used to maintain the structural stability of the MG state under acidic conditions. In this study trehalose was used as a penetrant, and intrinsic fluorescence spectroscopy and circular dichroism were performed to investigate the effects of a gradient concentration of trehalose on the structure of soybean 11S. The MG soybean 11S maintained a more α-helix structure (94.7%) and a larger hydrophobic area when treated with a high concentration of trehalose (1.3 mol/L) than when untreated, and retained a typical compact MG structure despite the lack of tertiary structural elements. A linear extrapolation model showed that the Gibbs free energy of the high-concentration trehalose-induced compact MG state of soybean 11S was reduced by 3 times, compared with the untreated globulin. This improvement of thermodynamic stability indicated that trehalose stabilized this structure by forming a stable trehalose–soybean 11S MG state system. With the addition of gradient trehalose, the surface tension of the solution was significantly reduced and the viscosity of the solution was increased. The emulsifying properties were optimized when the trehalose concentration was 0.5 mol/L, the emulsifying activity (EAI) and emulsifying stability (ESI) were 76.67 m2/g and 76.67%. The improvement of emulsifying property of 11S MG-trehalose system was further proved by observing the microstructure of emulsion by Cryo-SEM. This study advances the understanding of the 11S MG-trehalose system and provides a theoretical basis to produce proteins with excellent emulsifying properties.