Structural and functional regulation of soy protein isolate/sodium carboxymethyl cellulose complexes via surface...

This study investigates the interaction between soy protein isolate (SPI) and sodium carboxymethyl cellulose (CMC) at different pH levels and their emulsifying performance. The results show that decreasing pH led to a significantly increase in the particle size of SPI/CMC complexes, particularly below pH 3.0, which was attributed to enhanced electrostatic interactions and the formation of coacervates. Fluorescence and UV-Vis spectroscopy revealed noticeable shifts in the microenvironment of protein residues, indicating strengthened interactions between SPI and CMC with decreasing pH. The emulsions stabilized by SPI/CMC exhibited better stability and smaller droplet sizes at pH values of 4.4 and 4.0, whereas further reduction in the formation of larger aggregates, weakened interfacial adsorption, and reduced emulsion stability. Rheological and storage stability tests confirmed that emulsions prepared at pH 4.4 and 4.0 exhibited higher viscosity and enhanced storage stability. This study provides new insights into the role of pH in modulating the emulsifying behavior of SPI/CMC complexes, contributing to the design of stable and functional emulsifiers for food systems.