Soy protein isolate gel improved with carrageenan-assisted limited enzymatic hydrolysis: Gelation properties and binding abilities with selected flavour compounds

In this study, the aim was to explore the potential impacts of K-Carrageenan (KC) on the heat-induced gel properties, rheological properties, water-holding capacity, microstructure, and flavor absorption ability of Soy Protein Isolate (SPI) with varying degrees of hydrolysis (DH). The inclusion of KC notably enhanced the texture attributes, gel firmness, water holding capacity (WHC), and thermal stability of the composite gels, with particularly significant improvements observed at lower degrees of hydrolysis (DH6). It was found that SPI gels with high DH had poorer binding and release capabilities when compared to SPI gels with lower DH. However, when KC was added, the binding and release capacities of gels improved regardless of the DH. Moreover, the addition of KC and moderate hydrolysis together promoted the formation of compact gel structures in KSPH, resulting in a clear domination of elastic properties (G'>G″). The microstructure of the gels significantly influenced the adsorption rate of flavor compounds, with a higher adsorption rate achieved in KSPH composite gels that featured a more homogeneous gel network and smaller cavities. Moderate hydrolysis resulted in increased hydrophobic interactions, hydrogen bonding, and electrostatic interactions within the KSPH composite gels, which contributed to pyrazine flavor compound adsorption. The hydrophobic interactions were the primary forces among SPH, KC, and 2,5-dimethylpyrazine, which were affected by DH. This work offers a new perspective on the application of enzymatic treatment to regulate the adsorption rate and release capacity of protein-polysaccharide composite gels for flavor compounds, which is crucial for enhancing the gel properties in plant protein products and the flavor adsorption.