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.

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