DYNAMIC MECHANICAL ANALYSIS FOR GLASS TRANSITIONS IN LONG SHELF-LIFE BREAD

Dynamic Mechanical Analysis (DMA) showed three thermal transitions in meal, ready-to-eat (MRE) bread, resulting in various degrees of change in the viscoelastic property. The moisture-dependent transition at an extremely low temperature (-90-degrees-C to -50-degrees-C) was due to humectants added, while that at a higher temperature T1 was possibly due to ice melting and the polymer components. T1 increased from almost-equal-to -10-degrees-C at 29% moisture to almost-equal-to 150-degrees-C as moisture decreased to 2%. This correlated with hardening of the sample. A moisture independent transition at almost-equal-to 10-15-degrees-C by DMA was identified as a melting process of lipids (shortening). During storage, the magnitude of tan delta peak decreased but its peak temperature did not change. No evidence of any network could be observed by DMA throughout 3 yr storage.