Enhancement of gluconolactone-induced soybean protein isolate gels by low concentrations of oxidized konjac...

Gluconolactone (GDL) induces soybean protein isolate (SPI) gelation by gradually releasing H⁺, lowering the pH to promote protein aggregation. However, excessive GDL often lead to an undesirable acidic taste in food gels. This study evaluated the effects of oxidized konjac glucomannan (OKGM) and varying H⁺ release levels on SPI gel properties, aiming to enhance gel quality while reducing GDL dependency. Results demonstrated that OKGM significantly improved gel texture and viscoelasticity, with low concentrations (0.5-1.5%, w/v) promoting SPI aggregation and forming a denser, more elastic gel network. Notably, OKGM accelerated the gelation process, reducing the gelation time from 12.88 ± 0.14 to 11.26 ± 0.00 min, while also increasing gel strength and stability. Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) revealed that OKGM interacted with SPI through Schiff-base reactions, enhancing thermal stability. However, at high OKGM concentrations (2.0-2.5%, w/v), thermodynamic incompatibility led to phase separation, increasing surface hydrophobicity and free sulfhydryl content, which disrupted gel uniformity. Overall, OKGM synergized with GDL to induce gelation, enabling a reduction in acid coagulant usage while enhancing gel quality. This study provides a novel approach to designing low-calorie, fiber-rich SPI gels, offering a promising alternative to traditional soy gels in the food industry.