Mechanism of pH-driven gelation in Tremella fuciformis polysaccharide-soy protein isolate composite systems

The gelling properties of soy protein isolate (SPI) are limited, but can be enhanced by adding polysaccharides, with their interactions strongly influenced by pH. This paper explored the effects of pH (5-9) on gel mechanisms of Tremella fuciformis polysaccharide (TFP)-SPI complexes. Results showed that 1) at pH 7, the TFP-SPI composite gels exhibited superior rheological properties, hardness, water-holding behavior, and thermal stability whereas these properties were significantly destroyed under acidic/alkaline conditions, especially under acidic conditions; 2) the hydrophobic interaction of TFP-SPI composite gel was strong at pH 7 but decreased under acidic/alkaline conditions; 3) the hydrophobic and electrostatic interactions mainly drove TFP-SPI gel formation, particularly under neutral and alkaline conditions. In contrast, hydrogen bonds played the smallest role in the composite gels across conditions. Overall, the findings suggest that neutral pH favors TFP-SPI gel formation, offering guidance for designing heat-induced food gel systems, such as plant-based meat analogs or functional puddings.