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

BACKGROUNDMetal 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.RESULTSHere, the conformational conversion of SPI/SSPS induced by Na+, K+, Ca2+, Mg2+ and Fe3+ 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 beta-sheet of SPI/SSPS HIPEs increased with the addition of Ca2+, Mg2+ and Fe3+, 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.CONCLUSIONThese 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. (c) 2023 Society of Chemical Industry.