Effect of Wet Ball Milling on the Emulsion Properties of Aged Soybean Protein Isolate Analyzed from Structure Changes

Fresh soybean protein isolate (SPI) has poor stability, and its emulsifying and other functional properties deteriorate severely during storage and transport. In this article, wet ball milling was used to treat aged soybean protein isolate (ASPI) to study the changes in the structure and properties of ASPI. The mechanism of improving the emulsion properties of ASPI by wet ball milling was also investigated by analyzing the correlation between the structure and properties of ASPI and its emulsion properties. The results showed that after a short period of wet ball milling (3 min), the structure of ASPI unfolded, and the particle diameter decreased from 1380 to 1061 nm. The emulsion had a smaller volume-average droplet size (1.17 μm), a higher absolute value of ζ-potential (28.10 mV), and a lower flocculation index (19.01%). These showed that the appropriate wet ball milling could improve the emulsion properties of ASPI.