Influence of freeze-drying temperature and drying methods on selected properties of dried pumpkin
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| Authors: | Agnieszka Ciurzyńska1, Andrzej Lenart1, Patrycja Kawka1 1Department of Food Engineering and Process Management, Faculty of Food Science, SGGW – Warsaw University of Life Sciences ul. Nowoursynowska 159C, 02-776 Warszawa |
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| Abstract : | Pumpkin is a vegetable rich in nutrients, which can be a complement to a healthy, balanced diet. Due to the seasonality of the crop and the perishable nature of the material it is important to extend the shelf life of pumpkin. Freeze-drying is considered to be a method which allows obtaining product of good quality. Due to the removal of water at low temperature, most of the microbiological reactions are stopped, which allows to obtain high quality product. The paper presents the influence of temperature and freeze-drying method on selected physical properties of dried pumpkin. Frozen pumpkin cubes were subjected to freeze-drying for 24 hours at a constant pressure of 63 Pa and a safety pressure of 103 Pa, at shelf temperatures of 10, 40 and 70°C. Convective drying (at 50°C) and vacuum drying (50°C, pressure 4 kPa) were also conducted. For the dried materials obtained the following were assayed: water content and activity, colour, shrinkage, porosity, sorption properties. Freeze-drying temperature does not significantly affect the colour and shrinkage of the finished product. Freeze-drying at 70°C allows to obtain dried material with the lowest water activity. The highest porosity was noted for freeze-dried samples obtained at temperature of 10°C. Increasing the temperature of freeze-drying resulted in an increase of sorption properties of dried pumpkin. Freeze-drying allows to obtain dried material with the lowest water activity and shrinkage, and the highest porosity. Vacuum drying resulted in the best colour retention of the product, but the greatest shrinkage. Convective drying resulted in a very large shrinkage and lower porosity of the material, and deterioration of the sorption capacity. |
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| Keywords : | pumpkin, freeze-drying, convective and vacuum-drying, water vapour sorption, shrinkage, porosity, colour | ||||||||
| Language : | Polish | ||||||||