Osmotic dehydration of raspberries with vacuum pretreatment followed by microwave-vacuum drying

Defrozen raspberries were osmotically dehydrated in sucrose solution initially at low pressure (1.33 kPa for 8 min), and then at ambient pressure (4 h). Moisture decreased from 84% to 49% (wet basis), and almost one half of water removal occurred at the vacuum period. Two different transport coeffic...

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Bibliographic Details
Published in:Journal of food engineering 2010-07, Vol.99 (2), p.121-127
Main Authors: Bórquez, R.M., Canales, E.R., Redon, J.P.
Format: Article
Language:English
Subjects:
aqueous solutions
diffusivity
dried fruit
drying quality
heat transfer
heat transfer coefficient
mass transfer
microwave treatment
Microwave-vacuum drying
osmotic pressure
osmotic treatment
Osmotic-vacuum dehydration
pretreatment
Raspberries
Rubus idaeus
sucrose
thawing
vacuum processing
water activity
water content
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Summary:Defrozen raspberries were osmotically dehydrated in sucrose solution initially at low pressure (1.33 kPa for 8 min), and then at ambient pressure (4 h). Moisture decreased from 84% to 49% (wet basis), and almost one half of water removal occurred at the vacuum period. Two different transport coefficients were obtained: 19.9 × 10 −10 m 2/s for transport of water under vacuum, and 3.2 × 10 −10 m 2/s for water transport at atmospheric pressure. Losses of vitamin C were high (80%) and reutilization of sucrose solution is suggested. Osmotically dried raspberries were microwave-vacuum dried (1.33 kPa for 40 min) under on–off temperature control by varying microwave settings. An undamaged dried product (7.8% wet basis) of high quality (color, taste, structure) was obtained.
ISSN:0260-8774
1873-5770
DOI:10.1016/j.jfoodeng.2010.02.006