Influence of drying methods on selected physical and mechanical properties of straw-berries
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| Authors: | Iwona Sitkiewicz1, Dariusz Piotrowski1, Monika Janowicz1, Łukasz Szlendak1 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 : | The aim of this study was to determine the effect of drying methods on selected physical and mechanical properties of dried strawberries. Strawberries cv. Senga Sengana, thawed before the drying, were dried at 65oC using convective, vacuum (pressure in the dryer 4 and 16 kPa) and convective-vacuum drying methods; in the last method 50, 75 and 90% of the initial water content was removed at the stage of convective drying. Physical properties such as shrinkage and apparent density, and mechanical properties evaluated from compression and stress relaxation tests, such as compression work and relaxation modulus, were determined. The performed analysis showed that using the combined convective-vacuum drying methods allowed to obtain dried strawberries with shrinkage lower than 30%, low bulk density (0.1-0.15 g cm-3), and also with mechanical properties favourable for the consumers. The optimal degree of strawberries dehydration at the stage of convective drying prior to vacuum drying was 50% of the initial water content, which corresponds to specific humidity of about 3.70 g H2O (g d m)-1. |
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| Keywords : | strawberries, vacuum drying, convective-vacuum drying, shrinkage, bulk density, mechanical properties | ||||||||
| Language : | Polish | ||||||||