Abstract:

The effect of xylitol (0%–20%) on structural and functional properties of soy protein isolate (SPI) in phosphate
buffer solution was studied by assessment of solubility, surface hydrophobicity, intrinsic fluorescence intensity, secondary
conformational stability and foaming properties. The results showed that xylitol increased the solubility and decreased the
surface hydrophobicity and intrinsic fluorescence intensity of SPI, resulting in encasement of the tyrosine and tryptophan
residues initially exposed inside the protein molecule. In the presence of added xylitol, SPI exhibited a more compact and
periodical secondary structure. These structural modifications, consequently, led to impaired foamability of SPI. In addition,
an increase in the viscosity of SPI could be advantageous for enhancing its foam stability.

Key words: soy protein isolate, xylitol, protein structure, foaming properties