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vol. 17, nr. 2 (2011)
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The influence of temperature and pressure in vacuum-dryer chamber on rehydration of dried strawberries
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Agnieszka Ciurzyńska, Dariusz Piotrowski, Monika Janowicz, Iwona Sitkiewicz, Andrzej Lenart
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Department of Food Engineering and Process Management, Faculty of Food Sciences, Warsaw University of Life Sciences, SGGW ul. Nowoursynowska 159c, 02-787 Warszawa, Poland |
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vol. 17 (2011), nr. 2,
pp. 289-300
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abstract:
This work presents the influence of variety, diameter, pre-treatment and temperature or pressure changes in dryer chamber on rehydration properties of vacuum-dried strawberries. Strawberries variety Bounty and Pandora with diameters of 24 and 27 mm were used. Drying was realized in a laboratory vacuum-dryer with parameters: temperature 50, 60 and 70°C, pressure 4 and 16 kPa. Fruit drying was conducted to low water content level in dried material (below 10%). The analysis of influence of strawberry variety on rehydration showed that fruit variety Bounty obtained higher final water content after one hour immersion in water in comparison to variety Pandora. Increase of the diameter from 24 to 27 mm caused an increase of water content after rehydration, but only for Bounty variety. For Pandora variety the opposite effect was obtained. It was shown that fresh fruit vacuum-dried obtained almost five times lower water content after one hour of rehydration than fruit dried after defrosting. No unique influence of temperature changes on water content after rehydration was demonstrated. The increase of pressure during drying process from 4 to 16 kPa caused, in a majority of cases, water content decrease after one hour of rehydration. It was shown that decrease in pressure or temperature after rehydration resulted in obtaining higher final water content in comparison to opposite changes of drying parameters.
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keywords:
vacuum-drying, strawberries, rehydration, temperature, pressure
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original in:
Polish
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