Phase behavior and microstructure of preheated soy proteins and κ-carrageenan mixtures

Phase behavior and microstructure of preheated soy proteins (heat-induced aggregates)/κ-carrageenan (κ-car) mixtures have not been reported before. Hereby, heat-induced aggregates of different sizes and κ-car mixed systems were investigated in 0.1 M NaCl with pH 7.0 at room temperature (25 °C) with native soy protein/κ-car system as the comparison. Phase diagrams were established by centrifugation, chemical assays and visual observation and it was found that the larger aggregate/κ-car system had narrower stable region. The microstructures of the phase-separated mixtures were described using confocal laser scanning microscopy (CLSM), which revealed the association of protein aggregate structures after phase separation. The image analysis based on the CLSM images of different mixtures showed that the variance and the histogram of the gray values were different significantly. In addition, information of kinetics of phase separation was obtained from small deformation rheology (G′, G″).