Microalgae play a structuring role in food: Effect of spirulina platensis on the rheological, gelling characteristics, and mechanical properties of soy protein isolate hydrogel

Soy protein isolate (SPI) is a nutritional commercial product, while the poor solubility and mechanical properties restrict its applications to functional foods. As a biological resource, spirulina platensis is considered promising functional food component due to its balanced composition and various nutritional components. What's more, microalgae and their biopolymers are found to be structuring ingredients in food. Thus, in this study, the processed spirulina platensis was proposed to improve the rheological properties and mechanical properties of SPI hydrogel. The gel strength, hardness, and storage modulus of SPI gel can be significantly improved by adding spirulina platensis suspensions treated by pre-thermal and high-speed shearing homogenization. After food processing, cell wall polysaccharides of spirulina platensis were dissolved, which will be filled in the three-dimensional network of SPI hydrogel and increased physical interactions. Furthermore, the addition of spirulina platensis increases the content of β-sheet, thus improving the hardness and compactness of the SPI hydrogel structure. Overall, the successful synthesis of SPI-sp hydrogel provides a new idea for the food application of microalgae, which means that spirulina platensis can not only be ingested as a health product in the form of powder but also play a unique role in improving food texture as a structural component.