Gel properties of okara dietary fiber‐fortified soy protein isolate gel with/without NaCl

Abstract BACKGROUND Soy protein isolate (SPI) is widely used as an alternative to animal‐based protein, and its gelling property is essential for producing plant protein‐based foods. Insoluble dietary fiber has been used to improve the properties of protein gels. RESULTS Effects of partial replacement of SPI by okara dietary fiber (ODF) on the gelling properties of ODF‐fortified SPI gels with and without 0.1 m NaCl were investigated. The presence of ODF hindered the SPI self‐aggregation and reduced the surface hydrophobicity of SPI. The presence of ODF reduced the hydrophobic interaction and improved the proportion of disulfide bonds in the gels. In the microstructure, the swollen ODF promoted the local aggregation of SPI at 0.1 m NaCl. Texture profile analysis showed that 5% and 10% ODF improved the SPI gel hardness in the absence of NaCl, whereas only 5% ODF improved the gel hardness at 0.1 m NaCl. The results of low‐field nuclear magnetic resonance imaging revealed that ODF shortened the T 2 relaxation time of the free water in the gel. The gel of ODF‐10 had the highest storage modulus. CONCLUSION Using an appropriate amount of ODF to replace SPI could improve the quality of SPI gel and increase the dietary fiber content in the product. In addition, the appropriate ratio of ODF/SPI varied in different solution environments. © 2022 Society of Chemical Industry.