Metal cation‐induced conformational changes of soybean protein isolate/soybean soluble polysaccharide and their effects on high‐internal‐phase emulsion properties

Abstract BACKGROUND Metal ions commonly inevitably appear in food products and have adverse effects on high‐internal‐phase emulsions (HIPEs) foods, but conformational conversion of soybean protein isolate (SPI)/soybean soluble polysaccharide (SSPS) on the interface layer of HIPEs influenced by different metal ions has rarely been reported. RESULTS Here, the conformational conversion of SPI/SSPS induced by Na + , K + , Ca 2+ , Mg 2+ and Fe 3+ ions and its effects on HIPEs were investigated. After adding the ions to SPI and SPI/SSPS dispersions, the particle size and zeta potential results showed different degrees of flocculation; the zeta potential and Fourier transform infrared spectra indicated that SPI and SPI/SSPS changes in structure involve electrostatic interactions and hydrogen bonding. Moreover, Raman spectra showed that the content of β ‐sheet of SPI/SSPS HIPEs increased with the addition of Ca 2+ , Mg 2+ and Fe 3+ , suggesting that SPI molecules at the interface formed a more orderly structure. The ultraviolet and fluorescence results showed that the hydrophobic environment of tryptophan and tyrosine residues inside protein molecules played a vital role in the emulsifying stability of SPI. CONCLUSION These findings suggested that the SPI/SSPS complexes for food applications were not susceptible to ions, thus ensuring complex stability, showing potential for commercial application in the production of emulsions. © 2023 Society of Chemical Industry.