Effects of glycerol and moisture gradient on thermomechanical properties of white bread

The thermomechanical properties of breadcrumb were investigated using dynam ic mechanical analysis (DMA) and differential scanning calorimetry (DSC). T he main transition (T-1, near 0 degreesC) shifted to lower temperature with added glycerol due to freezing point depression. The low-temperature trans ition (T-3, similar to 50 degreesC), found only in high-glycerol (8.8%) bre ad, suggested that of excess or phase-separated glycerol. The high-temperat ure transition (T-2, 60-85 degreesC) appeared only in aged breadcrumbs; its temperature range was correlated well with the amylopectin melting transit ion (DSC) but its tan delta amplitude did not correlate well with the amylo pectin melting enthalpy (r(2) = 0.72). On the other hand, the change of E " (viscous behavior) suggested that T-2 might be related to the change in th e amorphous region. Domain-to-domain (amorphous) and crumb-to-crust moistur e migrations are two critical phenomenological changes associated with agin g and could lead to significant local dehydration of some amorphous regions contributing to mechanical firming during storage.