Effect of dry heat treatment of soy protein powder on aligned structure formation in soy protein-based food gels during freezing

The formation of aligned structures in a protein-based food gel through the freezing process depends on protein content, as proteins are crucial in creating rheological properties that closely resemble meat. These proteins contribute to the cohesive and resilient nature of plant-based meat substitutes by binding water, enabling the replication of the texture of real meat. This study was conducted to explore the impact of the water-binding ability of soy protein isolate (SPI) on the formation of aligned porous structures in soy protein-based food gels using the freeze alignment technique. Protein powders with different denaturation degrees can be prepared by dry heating SPI, resulting in powders with different amounts of soluble fraction and water-binding capacity. In this study, the frozen ratio, which quantifies the ratio of freezable water in the slurry, was used to assess the water-binding ability of the formulations. The degree of dry heating significantly affected the formation of ice crystals during freezing. As the solid content and water-binding ability increased, aligned pore formation was restricted. Fast Fourier transform (FFT) analysis was conducted on the microscopic images of freeze aligned products, revealing a significant impact of the water-binding ability on anisotropic pore structure formations. In the present study, the application of the dry heat treatment at 70 °C and 70% relative humidity, along with a formulation having 10% solid content, showed a higher potential for replicating the anisotropic structure of meat analogs.