Effect of osmotic dehydration on mechanical properties of freeze-dried strawberries was shown. As investigation material Senga Sengana strawberries about 25-30 mm diameter were used. The osmotic solutions with water activity about 0,9 (sucrose solution 61,5%, glucose 49,2%, starch syrup 67,5%) were used. Osmotically dehydrated fruits were freeze-dried in heating shelves temperature 10, 30, 50 and 70°C for 24 hours. Dried strawberries were compressed to get 25% buckle initial height of freeze-dried fruits. Differences between compression curves dependent on the kind of osmotic solution were found. There was shown that after osmotic dehydration there is essential increase of compression force for freeze-dried fruits. For freeze-dried strawberries osmotically dehydrated in sucrose solution, stored in chambers with water activity solution about 0,225-0,648 the biggest compression force was needed to get demanded buckle. The influence of freeze-drying temperature on compression force of freeze-dried strawberries without osmotic dehydration was investigated. There was shown that freeze-drying in temperature 30°C cause decrease compression force for dried fruits to compare with freeze-dried strawberries in 10, 50 and 70°C. For dried fruits water activity and water contain was investigated to.
freeze-drying, strawberries, osmotic dehydration, mechanical properties