Water properties in wheat flour dough II: classical and knudsen thermogravimetry approach

Thermo-Gravimetric Analysis (TGA) investigations suggest that water in a wheat flour dough is partitioned in various states related to the different disperse phases of the system. Classical TGA results indicate the gross water partition at the macroscopic level, while Knudsen TGA investigations, that allow evaluation of the relative humidity of the dough at room temperature, suggest the involvement of water in the structure of the dough at a supra-molecular level. The overall moisture content, the mechanical stresses and the presence of extra non-starch polysaccharides and/or soluble proteins, can affect this partition, either promoting water displacements across the inter-phases, or modifying the supra-molecular structure of the system. The investigations, extended to bread crumb during ageing, indicate that water undergoes displacements and forms stronger links with the components of the aged crumb with a kinetic law that can be influenced by the presence of extra non-starch polysaccharides.