Color Stability of Freeze-dried Date Fruits (Barhi CV.) during Storage

Fresh Date fruits “Barhi CV.” were freeze dried as slices to characterize the dried fruit quality. CIELAB
color parameters (L*, a*, and b*) were measured as well as Chroma, the hue angle, the browning
index and the total color difference parameters were derivative. The samples were stored for 12
months at three temperatures of 5, 15 and 25°C with an uncertainty of ±1°C to assess the color
change kinetics and quantify the degree of change during storage. The L*, a* and b* values for fresh
samples at room temperature were 93.16±0.15, 18.76±0.45 and 61.70±0.32, respectively, while they
were 78.72±0.51, 29.52±0.07 and 62.75±0.14 after 12 months.
To explain the changing kinetics of the date slices, zero, first and second order models were
attempted. Based on statistical analysis, the first-order model was found to be the best model for all
CIELAB parameters. Analysis on the kinetic constants reveals that the temperature could affect the
resulting color of the dried product, in turn, it contributes to the color changes of the freeze dried
Barhi during storage. The values obtained for the activation energy for freeze-dried Barhi based on
the selected models were between 4930 and 10850 kJ. mol-1 which were somewhat different from
the reported values due to the variation in sample’s type, treatment or process. In the present study,
Barhi fruit slices were freeze-dried (FD) and examined. The effect of the FD process on the color
change, water activity, and moisture content was determined over 12-month storage time. Based on
the experimental data, all CIELAB color parameters were significantly affected by temperature and
storage time. Based on the statistical analysis, the first-order model could be used to fit the data for of
color change in freeze-dried Barhi fruit slices.