Rheological investigation and molecular architecture of highly hydrated gluten networks at subzero temperatures

The structural properties and ultra morphology of highly hydrated gluten networks at subzero temperatures were studied. Modulated differential scanning calorimetry (MDSC), mechanical spectroscopy in the form of dynamic oscillation on shear, and transmission electron microscopy (TEM) were employed as analytical tools. The experimental protocol documented the absence of a well-defined glass transition region in terms of overall spectrum shape and temperature band. Thus the reversing component of heat flow recorded using MDSC shows that a series of overlapping glass transition phenomena are spread over a broad temperature range. Furthermore, calorimetrically observed relaxation mechanisms do not correlate in the temperature domain with mechanical functions, an outcome that argues that there is no direct link between the mechanical stability and calorimetrically recorded molecular processes. In the absence of a distinct glass transition region, it is proposed that ice melting could be considered as the sole valid indicator of molecular mobility and quality control for frozen hydrated gluten. The ultra morphology of networks in these systems is made of flat sheets/thin films being ruptured by ice formation and subsequent recrystallization.