Effects of Modification Technology on Soybean Protein Isolate: Physicochemical Characteristics, Protein Conformation, and Gel Properties

Plant-based protein products hold a crucial position in the food industry in response to the demand for sustainable development. The effects of pH-shifting, fibrillation treatment (SPF), and mild heating on the physicochemical characteristics, protein conformation, and gel properties of soy isolate protein (SPI) were studied. The result showed that pH-shifting induced a reduction of the smallest particle size from 323.18 to 156.21 nm and the largest total sulfhydryl from 78.56 to 98.45 µmol/g. Compared to the control, the viscosity increased and surface hydrophobicity decreased after modification treatments. Fourier transform infrared spectroscopy and intrinsic fluorescence spectroscopy suggested that the three modification methods significantly changed the secondary and tertiary structure of SPI. In addition, it was found that pH-shifting induced the gel to form a denser gel network structure with favorable gel strength (27.09 g), water holding capacity (98.65%), and thermostability, while SPF induced the gel network to form a loose structure. Thus, modification techniques, particularly pH-shifting, can be effectively employed to enhance the gel properties of SPI. PRACTICAL APPLICATIONS: SPI is highly favored in the food industry due to its nutritional value and sustainability. However, its solubility is low due to its compact structure, which limits its application in the food industry. Modifying proteins with different methods to improve their functional properties holds great significance for the development of plant-based gel foods. This provides valuable insights into optimizing the performance of SPI gel products and promoting the growth of the sustainable plant-based food sector.