The thermal aggregation behavior and functional properties of SPI-catechin complexes under spray-drying conditions

Commercial soy protein isolates (SPI) often suffer from poor solubility and diminished functional properties due to the harsh conditions of spray-drying. This study demonstrated that catechin complexation effectively modulated SPI thermal aggregation behavior during spray-drying conditions. Structural characterization revealed that incorporating catechin (0.25%-1.75%, <i>w/w</i>) promoted a conformational transition in SPI from predominantly random coil structures to more ordered <i>α</i>-helical configurations. Fluorescence spectroscopy and electrophoresis results suggested hydrophobic interactions dominated between SPI and catechin. Notably, at 1% catechin, thermal aggregation was notably mitigated, transforming insoluble aggregates into soluble ones stabilized by electrostatic forces. At this optimal concentration, SPI solubility improved by 181.09% compared to commercial SPI, while emulsifying activity, thermal stability, and foaming stability were also markedly enhanced. Moreover, at 0.25% catechin, gel hardness reached 1.58 ± 0.02 N, higher than in other groups. Disulfide bonds and hydrophobic interactions were found to be key in forming the gel network.