Panification sans gluten

Abstract

This work aims to locate at the structural and molecular scale the rheological and technological responses of gluten-free bread doughs compared to those control of soft wheat in order to know the molecular interactions involved and to know how to exploit them. The rheological properties of the doughs as well as the technological properties of their breads were estimated. The response surfaces methodology was used for the optimization of the methodology of chemical dissociation of molecular interactions. The validation of the latter was carried out by a classification test of bread doughs of différent qualities followed by a statistical test of correlation between the dissociation rates of doughs and their rheological and technological quality parameters. The effect of molecular interactions on the rheological behavior of doughs was approached by the inhibition of S-S bridges formation by NEMI and the dissociation of hydrophobic interactions by SDS. This same principle was followed for the study of the impact of molecular interactions on the establishment of gluten-free bread dough. The structural mechanism of gluten-free bread doughs development was studied by FT-IR and FT-Raman spectroscopie methods. Gluten-free doughs show higher elastic behavior than that of soft wheat, thus inducing their low viscoelasticity. The optimum SDS and P-mercaptoethanol concentration ranges allowing a maximum dissociating effect are respectively [0-3.5]% and [0-0.007] M for 60 min of contact at rest between dough and dissociating solution. The highest dissociation rates are noted respectively for Maize- Field bean, Rice- Field Bean, Soft wheat dough type 1 and then type 2. The low viscoelasticity of gluten-free doughs is the resuit of their poor ability to develop S-S bridges and hydrophobic interactions. Hydrophobic interactions participate in the formation of gluten-free matrices more than S-S bridges. The mechanism for the formation of gluten-free protein network was based on the formation of P-sheet and a-helix structures to the détriment of P-turns. This is favored by the strong absorption of water during the long kneading time. Gluten-free proteins are characterized by a strong tendency to form S-S bridges of unstable conformations. The latter condition the distribution of secondary structures involved in the maintenance of gluten-free protein networks and consequently the solid character and the low viscoelasticity of their doughs. The strong ability of starches in gluten-free ingrédients to group in a crystalline form conditions the strong structuring and strong folding of their protein networks.