Enzyme-crosslinked soy protein aerogels: Structural and functional modulations by pre-freezing process

Biopolymer aerogels, particularly protein-based aerogels, have garnered significant attention due to their environmentally friendly nature, high porosity, and unique functional properties. However, the production of soy protein isolate (SPI) aerogels using SPI as the sole precursor material is still challenging, particularly in achieving the desired structural and functional properties. Herein, the effect of different pre-freezing temperature (−20 °C (A20), −80 °C (A80), and −196 °C (A196)) on structural and functional properties of single-component SPI aerogels is investigated. The single-component SPI aerogels are prepared by transglutaminase (TGase)-crosslinked SPI hydrogels as precursors and then pre-frozen at different temperatures. Among three aerogels, A80 aerogel exhibits the highest structural integrity, featuring an interconnected, dendritic pore structure, which results in the most extensive pore size distribution and the highest porosity of 92.67 ± 0.53 %. In contrast, A196 demonstrates the most compact microstructure and the most concentrated pore size distribution, with the lowest porosity of 90.43 ± 0.28 %. Importantly, the pre-freezing treatment significantly influences the structural properties of SPI aerogels. A196 aerogel shows less ordered structures, with a higher presence of β-turns and random coils, compared to the more ordered structures observed in A20 and A80 aerogels. Moreover, A196 aerogel exhibits the best oil adsorption capacity (OAC) and oil holding capacity (OHC), while A80 aerogel demonstrates the highest dye adsorption. These findings provide new insights into the fabrication of single-component TGase-crosslinked SPI aerogels.