BACKGROUND Traditional soy protein gel products such as tofu, formed from calcium sulfate or magnesium chloride, have poor textural properties and water retention capacity. Soy glycinin (SG) is the main component affecting the gelation of soy protein and can be cross‐linked with polysaccharides, such as sugar beet pectin (SBP), and can be modified by changing system factors (e.g., pH) to improve the gel's properties. Soy glycinin/sugar beet pectin (SG/SBP) complex double network gels were prepared under weakly acidic conditions using laccase cross‐linking and heat treatment. The structural changes in SG and the properties of complex gels were investigated. RESULTS Soy glycinin exposed more hydrophobic groups and free sulfhydryl groups at pH 5.0. Under the action of laccase cross‐linking, SBP could promote the unfolding of SG tertiary structures. The SG/SBP complex gels contained 46.77% β‐fold content and had good gelling properties in terms of hardness 290.86 g, adhesiveness 26.87, and springiness 96.70 mm at pH 5.0. The T22 relaxation time had the highest peak, and magnetic resonance imaging (MRI) showed that the gel had even water distribution. Scanning electron microscopy (SEM) and confocal scanning laser microscopy (CLSM) indicated that the SG/SBP complex network structure was uniform, and the pore walls were thicker and contained filamentous structures. CONCLUSION Soy glycinin/ sugar beet pectin complex network gels have good water‐holding, rheological, and textural properties at pH 5.0. The properties of soy protein gels can be improved by binding to polysaccharides, with laccase cross‐linked, and adjusting the pH of the solution. © 2022 Society of Chemical Industry.

BACKGROUND Soy protein isolate (SPI) can be used as an emulsifier to stabilize emulsions, though SPI is unstable under low acidic conditions. Stable composite particles of SPI and dextran sulfate (DS) can be formed by the electrostatic interaction at the pH 3.5. Furthermore, the SPI/DS composite particles can be used to prepare a high complex concentration emulsion. The stabilization properties of the high complex concentration emulsion were investigated. RESULTS Compared to uncompounded SPI, the particle size of SPI/DS composite particles was smaller at 1.52 μm, and the absolute value of the potential increased to 19.9 mV when the mass ratio of SPI to DS was 1:1 and the pH was 3.5. With the DS ratio increased, the solubility of the composite particles increased to 14.44 times of the untreated protein at pH 3.5, while the surface hydrophobicity decreased. Electrostatic interactions and hydrogen bonds were the main forces between SPI and DS, and DS was electrostatically adsorbed on the surface of SPI. The emulsion stability significantly enhanced with the increase of complex concentration (38.88 times higher than at 1% concentration), the emulsion average droplet size was the lowest (9.64 μm), and the absolute value of potential was the highest (46.67 mV) when the mass ratio of SPI to DS was 1:1 and the complex concentration of 8%. The stability of the emulsion against freezing was improved. CONCLUSION The SPI/DS complex has high solubility and stability under low acidic conditions, and the emulsion of the SPI/DS complex has good stability. © 2023 Society of Chemical Industry.

Soy glycinin (SG) and sugar beet pectin (SBP) were cross-linked using laccase to form a complex SG/SBP (SP) and then combined with lysozyme under the heating condition to form SP/lysozyme composite gels. The properties of SP/lysozyme composite gel and its inhibition on Staphylococcus aureus were investigated. Results revealed that the zeta potential changed from −32 to 8.2 mV upon adding lysozyme, its morphology was larger, and the particle size and turbidity increased. The Fourier transform infrared spectroscopy and X-ray diffraction results indicated that the interactions between SP and lysozyme were electrostatic interaction and hydrogen bonding. The mechanical properties showed that the SP/lysozyme composite gel could recover its original shape after 90% strain compression when SP/lysozyme was 10:4 and 10:5, and the storage modulus (G′) was higher at 10:5 about 105 Pa. Scanning electron microscopy results showed that the granular size increased, and the antibacterial property on S. aureus was enhanced.