Comparison of lipid effects on structural features of hard and soft wheat flour proteins assessed by front-face fluorescence

Front-face fluorescence was used to assess changes in the structural features of proteins in wheat flour dough upon addition of different exogenous lipids. Structural changes resulting from the solvation of proteins and from the mechanical deformation of proteins in dough or dough containing lipids were measured. The effects of lipid type and addition on changes in overall protein surface hydrophobicity were estimated by titrating soft and hard wheat flours, mixed with water and varying the lipid levels, with increasing concentrations of the fluorescence hydrophobic probes 1,8 anilino-napthalene-sulphonate (ANS) and thioflavin T. The lipid type and level modified the exposure of the probe to the solvent. The effects of lipids were more apparent with soft wheat flour having low-affinity hydrophobic sites on the protein surface. The dough was then characterized upon consistent mixing and physical modification in the farinograph at constant water and ANS/thioflavin T concentration, while varying the type and amount of lipids. Lipid-dependent shifts toward longer wavelengths in the probe fluorescent emission with low-protein flour suggest differences in protein coating effects related to lipid structure and protein quality.