Abstract: In this study, the emulsion formed during enzyme-assisted aqueous extraction of soybean oil was investigated at different hydrolysis times (1, 2, and 3 h) and enzyme dosages (1% and 2%). The mechanism of action of oil droplets in the emulsion was elucidated to explore the structural features and intermolecular interactions. The degree of hydrolysis (DH), microscopic observation, zeta-potential, fluorescence spectroscopy, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles were determined. The results showed that the DH of the emulsion was about 7%. As a result, the protein in the emulsion was broken down into small peptides, resulting in reduced affinity between oil and protein, droplet aggregation and decreased absolute value of zeta potential. Large protein aggregates linked by disulfide bonds appeared on the SDS-PAGE. In addition, the fluorescence intensity of the emulsion was obviously weakened as compared to soybean protein isolate (SPI) under the same hydrolysis conditions, which may be attributed to the presence of phospholipids, the interaction between tryptophan residue and oil and the disulfide-linked aggregates.

Key words: emulsion, structure characteristic, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), fluorescence spectroscopy, intermolecular interaction