Original scientific paper
The influence of temperature on rehydration and sorption properties of freeze-dried strawberries
Agnieszka Ciurzyńska
; Warsaw University of Life Sciences, Faculty of Food Sciences, Warszawa, Poland
A. Lenart
; Warsaw University of Life Sciences, Faculty of Food Sciences, Warszawa, Poland
Abstract
The aim of this work was to investigate the influence of heating shelf temperature on selected physical properties of freeze-dried strawberries. Frozen strawberries were freeze-dried at heating shelf temperature of 10, 30, 50 and 70°C for 24 hours.
Rehydration, adsorption rate and sorption isotherms were determined for freeze-dried strawberries. With increase the temperature of heating shelves in the range 10-50°C, rehydration capacity was increased. After 30 minutes of the rehydration process there was a decrease in water content, which is probably connected with changes in structure. Sorption isotherms were included to II isotherms type and have a sigmoidal shape characteristic for most food products. For the mathematical description Peleg’s model was used. For freeze-dried strawberries obtained in the range from 10 to 50°C isotherms have the same courses. Increase of temperature to 70°C resulted in obtaining the lowest water content in the water activity range from 0.113 to 0.648. There is a statistically significant influence of temperature of heating shelf on water vapour sorption for freeze-dried strawberries. For fruit freeze-dried in 30°C there was the highest water vapour sorption rate.
Keywords
strawberries; freeze-drying; water sorption; kinetic; rehydration
Hrčak ID:
53240
URI
Publication date:
8.7.2009.
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