Ball-milling changed the physicochemical properties of SPI and its cold-set gels

- Soybean protein isolate (SPI) was treated by mixer ball mill (BM).
- BM changed the secondary structure, tertiary structure and particle size of SPI.
- BM increased the gel strength and water holding capacity of SPI cold-set gels.
- Appropriate BM treatment can improve the gelation property of SPI cold-set gels.

In this study, the effect of ball-milling (BM, Mixer Mill MM 400) treatments on the physicochemical properties of soybean protein isolate (SPI) and its cold-set gels induced by glucono-δ-lactone was studied. BM of SPI increased the gel strength and water holding capacity of cold-set gels significantly after 4 min of BM treatments. BM treatments did not alter the primary structure of SPI, but caused minor changes of the secondary structure. Furthermore, surface hydrophobicity of SPI increased gradually from 2058 to 5051 after 10 min of BM, while free SH groups reduced from 3.92 to 2.65 μmol/g protein. Moreover, near-UV CD spectra indicated that the tertiary conformation stability was increased and the hydrophobic groups might shift to a more hydrophobic microenvironment. In conclusion, appropriate BM treatments could change the physicochemical properties of SPI and increased the gelation properties of SPI cold-set gels.

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