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.