Denaturation of soy proteins in solution and at the oil-water interface: A fluorescence study

Structural changes ensuing from denaturation of soy proteins in solution or occurring at the oil-water interface were studied by fluorescence spectroscopy. Studies were carried out on solutions and emulsions stabilized with beta-conglycinin or glycinin. Tryptophan fluorescence spectroscopy was used to evaluate tertiary structural changes. The binding of fluorescent dyes and the accessibility of reactive cysteine thiols were also used to better identify structural changes of these proteins in solution. Protein conformational changes after interaction with the hydrophobic oil surface were compared with those ensuing from physical (temperature) or chemical denaturation (chaotropes). Results from solution denaturation experiments indicate that structural changes of beta-conglycinin by both temperature and chaotropes are reversible under appropriate conditions, and result in a rearrangement of the supra-macromolecular assembly of the protein structure. On the other hand, glycinin treated under the same conditions undergoes irreversible denaturation in solution at temperatures well below 90 degrees C. Both proteins undergo partial denaturation after adsorption on the lipid surface, and no further denaturation occurs upon heating of the emulsions prepared with either protein. (C) 2010 Elsevier Ltd. All rights reserved.