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Color and Water Activities Changes of Roselle Coated Rice under Low Relative Humidity Air Drying

2012-09-12 1211

Color and Water Activities Changes of Roselle Coated Rice under Low Relative Humidity Air Drying

The main objectives of this study was to investigate the changes in color and water activities of the dried roselle coated rice using the low relative humidity air drying. The drying conditions include: air temperatures of 40-80oC, relative humidities of 23-25% and inlet air velocities of 0.1-0.5 m/s, respectively. The parameters for the color of roselle coated rice were determined using Hunter L, a, b value, chroma, Hue and total color difference. The drying process changed all three color parameters (L, a, b) causing a color shift towards to lighter region. The value of b was decreased while L- and a-values were increased during drying. Comparing the product drying, it was observed that the roselle coated rice dried using low relative humidity air tray dryer were better in color compared to those dried under the common hot air. Water activities were approximately 0.3-0.5. In conclusion, overall performance of roselle coated rice dried at 40oC, 23-25%R.H. and 0.5 m/s was the best with respects to color and water activity.

Authors : Pathto, P,Meeso, N.,Siriamornpun, S.
Book /Journal Title : Agricultural Sci. J. ;2010 / 41 / 189-192

 

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