Thermal unfolding of gelatin in solids as affected by the glass transition

The thermal unfolding or denaturation of solid-state proteins during processing can affect their functionality. This project explored the relation between the glass transition temperature (T(g)) and thermal unfolding temperature (T(m)) using gelatin as a model system. Freeze-dried gelatin was prepared containing various polyol types at several concentrations. Using differential scanning calorimetry, T(m) and T(g) were determined. Moisture and polyols (that is, glycerol, xylitol, sorbitol, sucrose, and trehalose) promoted a lowering of both T(g) and T(m), the extent of which depended upon the plasticizer type and concentration. For all the data, T(m) > T(g), and a plot of T(m) against T(g) indicated a linear relationship (R(2) = 0.95). These results suggest that formulations must be in the rubbery state to have the necessary mobility for hydrogen bond disruption that leads to protein unfolding. Glass transition data should be considered when developing processing parameters for proteinaceous systems.