Investigation of viscoelastic behaviour of rice-field bean gluten-free dough using the biophysical characterization of proteins and starch: a FT-IR study

Gluten-free bread making success is closely linked to the biophysical behaviour of dough. Quality of these doughs is largely determined by the properties of their proteins and starch. This study aimed to explain, at the structural level the rheological behaviour of gluten-free rice-field bean dough compared to that of soft wheat. The conformational aspects of proteins and starch were studied using Fourier transformed infrared spectroscopy (FT-IR). Doughs of soft wheat, rice, field bean, mixture of rice-field bean flour and the same mixture where a portion of rice flour underwent hydrothermal treatment were studied. The results show that viscous and viscoelastic components of gluten-free doughs were changed by supplementation of rice with field bean flour. Most of gluten-free doughs possessed a higher storage modulus in comparison with soft wheat dough. Analysis of FT-IR spectra in the amide I region conveyed to find the differences relative to soft wheat flour dough showed that in non-gluten doughs the increase in beta-sheet content was observed at the expense of beta-turns. These results were confirmed by amide I deconvolution. Gluten-free doughs contained more beta-sheet structure as compared to soft wheat dough and less beta-turns inducing high structuralization level that characterized this type of dough matrix. Concerning starch, the supplementation with rice-field bean generated the reorganization of field bean and rice doughs starches approaching that of wheat dough.