Mechanism of Solubility Enhancement of Soybean Protein by High-Energy Fluidic Microfluidizer

In order to investigate the modification effect of high-energy fluidic microfluidizer (HEFM) treatment on plant protein after and clarify its solubilization mechanism, a 5% (m/m) aqueous suspension of soybean protein was treated using a HEFM under different pressures (30, 60, 90 and 120 MPa), obtaining modified soybean protein. The physicochemical and structural changes of soybean protein after the treatment were characterized by solubility measurement, particle size analysis, fluorescence spectroscopy, circular dichroism spectroscopy and electrophoresis. The results showed that the solubility of treated soybean protein increased significantly with increasing pressure, reaching 76.97% at 120 MPa. Changes in microstructure and protein size showed that HEFM promoted the disintegration of large aggregates of soybean protein. As the pressure increased from 0 to 120 MPa, the particle size D[4,3] decreased from 94.90 to 3.65 μm, the absolute value of the zeta potential increased from 18.40 to 28.03 mV, the surface hydrophobicity increased from 1 559.60 to 7 199.28, the content of free sulfhydryl increased from 18.87 to 22.18 μmol/g, and the secondary structure shifted from β-sheet to α-helix. This study showed that HEFM technology can effectively modify the structure of soybean protein leading to improved solubility, which provides theoretical support for the industrial solubility modification of plant protein.