Structural and physical properties of soybean protein isolate films with ohmic heating treatment: Impacts of electric field

Abstract

The effects of ohmic heating (OH) and conventional heating (CON) on the structural and physical properties of soybean protein isolate (SPI) and SPI films were studied. When the electric field was varied from 0 to 12 V·cm−1, the fluorescence intensity, average particle size, and polydispersity index (PDI) of the OH-SPI were the least at 9 V·cm−1 and increased thereafter. Meanwhile, the free SH-group content and surface hydrophobicity were the maximum at 9 V·cm−1 and decreased thereafter. Moreover, the α-helix content decreased and the random coil content increased noticeably at 12 V·cm−1. In terms of the properties of the SPI films, the mechanical properties and water resistance of the OH-SPI films were superior to those of the CON-SPI films. When the electric field was 9 V·cm−1, the tensile strength of the OH-SPI film increased from 2.76 MPa to 4.34 MPa, and the elongation at break of the OH-SPI films improved. Moreover, the water resistance of the OH-SPI films was the best at this electric field.