Different commercial soy protein isolates and the characteristics of Chiba tofu

Twenty different cold gels were made by adding transglutaminase enzyme and using soy protein isolate (SPI) powders from different manufacturers to investigate their potential as an ingredient in Chiba tofu. The study showed that SPI gives Chiba tofu high hardness and springiness, and excellent quality when its sulfur-containing amino acid content is >2.83%, β-sheets content is >52.1% and the 11S:7S ratio is > 1.88. Moreover, low field nuclear magnetic resonance confirmed that the water mobility of the best sample left more water in the gel network. Intermolecular force results indicated that the hydrophobic interactions, disulfide bonds and non-disulfide covalent bonds were the main chemical forces maintaining the structure of the gel network. The scanning electron microscopy showed that the best Chiba tofu sample had a more continuous and uniform gel network structure. Overall, the characteristics of SPI have an important influence on the quality of Chiba tofu.