Characteristics of soy protein isolate gel induced by glucono-δ-lactone: Effects of the protein concentration during preheating

In order to explore ways to improve the quality of the cold-set gel of soy protein, soy protein isolate (SPI) with different concentrations was preheated to produce soluble SPI aggregates (SSA), of which the gelation processes induced by glucono-δ-lactone (GDL) and gel properties were investigated in this study. The results showed that with the increasing SPI concentrations, the SSA showed increment in the particle size and quantity of net surface charge, accompanied with reduction in the surface hydrophobicity. During the acidification process, compared with the SSA generated from SPI of 20 mg/mL, the SSA produced from SPI of 60 mg/mL exhibited a slower intermolecular binding in the “pre-aggregation” stage, but was preferred to form beaded aggregates rather than irregular protein clusters, which led to earlier gelation onset and a more uniform gel network; the hardness, elasticity, water holding capacity and toughness of the resulting gel were also increased. Besides, with the rise of SPI concentrations for preparing SSA, the disulfide bond in the gel structure was strengthened. Therefore, adjusting the characteristics of SSA such as its charge states through controlling the preheating process could be utilized to regulate the properties of the acid-induced SPI gel, so as to help improve the quality of cold-set gel products of soy protein.