Improved Low pH Emulsification Properties of Glycated Peanut Protein Isolate by Ultrasound Maillard Reaction

In this work, peanut protein isolate (PPI) was grafted with maltodextrin (MD) through the ultrasound-assisted Maillard reaction. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed a link between PPI and MD. The substantially increased accessibility of the major subunits (conarachin, acidic subunit of arachin, and basic subunit of arachin) in PPI under high-intensity ultrasound treatment led to changes in the degree of graft (DG), zeta-potential, protein solubility, and surface hydrophobicity of conjugates. Emulsion systems (20% v/v oil, 2.0% w/v PPI equivalent, pH 3.8) formed by untreated PPI, PPI-MDC (PPI-MD conjugates obtained with wet-heating alone), and UPPI-MDC (PPI-MD conjugates obtained with ultrasound-assisted wet heating) were characterized using a light-scatter particle size analyzer and confocal laser scanning microscope. Results showed that emulsions of untreated PPI and PPI-MDC were not stable due to immediate bridging flocculation and coalescence of droplets, whereas that formed by UPPI-MDC with 32.4% DG was stable with a smaller mean droplet size. It was believed that high-intensity ultrasound promoted production of glycated PPI, which was soluble and surface active at pH 3.8 and thus improved emulsification properties for UPPI-MDC. This study shows that glycated PPI by ultrasound-assisted Maillard reaction is an effective emulsifying agent for low pH applications.