State diagram of temperature vs date solids obtained from the mature fruit

Mature dates were dried achieving an increase in the level of solids from 70.8% to 92.4% (wet basis). Small deformation dynamic oscillation was employed to identify changes in the viscoelastic properties of dates as a function of solids. Samples were cooled or heated at a constant scan rate of 1 degrees C/min. At high temperatures, e.g., 70 degrees C, the storage and loss modulus (G' and G ", respectively) remained relatively independent of the time or frequency of observation, thus delineating the plateau zone. Cooling resulted in rapid development of both moduli with G " overtaking G'. This is known as the glass transition region and was used to define the rheological T-g. Eventually, the glassy state is reached where the storage modulus becomes dominant once more and approaches values of 10(9.5) Pa. The values of T-g were used to determine the metastable glass transition curve of mature dates. At lower levels of solids, i.e., between 11.7% and 64%, freezing experiments were employed to identify the equilibrium melting curve of ice. The state diagram yielded a maximally freeze-concentrated solute at 70% solids with the characteristic temperature of glass formation being -50 degrees C. Data on equilibrium and kinetic events were modeled using the Chen and Gordon-Taylor equations yielding the rheological T-g for date solids at their effective molecular weight.