Revealing the role of λ-carrageenan on the enhancement of gel-related properties of acid-induced soy protein isolate/λ-carrageenan system

This work explored the pivotal role of λ-carrageenan in fortifying the gel structure, consequently enhancing gel-related attributes within an acid-induced soy protein isolate/λ-carrageenan system (SPI/Car). The model system was prepared by subjecting a thermally treated mixture of these two biopolymers to acidification. Small-angle X-ray scattering (SAXS) and chemical force analysis unveiled the profound influence of hydrogen bonding and electrostatic interactions in the formation of the intricate network architecture of SPI/Car gels. Remarkably, λ-carrageenan interacted with the hydrophilic groups on the surface of agglomerated SPI particles, effectively composing the fundamental framework of SPI/Car gels. Simultaneously, λ-carrageenan emerged as a linchpin through hydrogen bonding, establishing pivotal crosslinking connections. The introduction of λ-carrageenan resulted in a reduction in SPI particle size, the dispersion of previously formed aggregates, and a subtle blurring of the SPI particles. It also significantly heightened the prevalence of hydrogen bonding and electrostatic interactions, ultimately giving rise to a robust yet somewhat coarse gel structure, as evidenced by confocal laser scanning microscopy (CLSM). These profound structural alterations underpinned the enhancement of water-holding capacity (WHC) and gel hardness in SPI/Car gels. These findings hold promise for the rational design and application of SPI-based systems in the production of processed vegetarian and vegan foods.