Enhancement mechanism of ι-carrageenan on the network structure and gel-related properties of soy protein isolate/λ-carrageenan system

Enhancement mechanism of ι-carrageenan on the network structure and gel-related properties of soy protein isolate (SPI)/λ-carrageenan system was investigated. Adding ι-carrageenan decreased SPI particles' size in nano-scale, reduced hydrophobic interactions by suppressing exposure of hydrophobic groups, and increased the disulfide bonds in SPI. With rising ι-carrageenan content (< 0.55 %), the interaction between ι-carrageenan and SPI was enhanced mainly through electrostatic interaction and hydrogen bond. Meanwhile, SPI particles were reduced and their stacking compactness was increased as well. These contributed to the improvement of network structure and thus increased weakly bonded water from 97.7 to 98.5 %, water holding capacity from 55.29 % to 61.70 % and gel hardness from 0.53 to 1.30 N. Higher ι-carrageenan content (> 0.55 %) induced micro-phase separation as shown by CLSM images, and led to reduction of gel hardness. These results favor the rational design and application of SPI-based gel systems with desired practical properties.