Wpływ obróbki wstepnej przed suszeniem konwekcyjnym na właściwości reologiczne suszonej cebuli

W pracy wykazano, że obróbka wstępna przed suszeniem konwekcyjnym, zmieniając skład chemiczny, modyfikuje właściwości mechaniczne suszonej cebuli.

The aim of this work was to investigate the effect of pre-drying treatment on rheological properties of onion. Raw material used for the tests were the Błońska and Oporto varieties. Prior to convective drying at 60°C the onions were subjected to pretreatment consisting in soaking in water, osmotic dehydration in sucrose solution, dipping in 1% solution of starch gruel with addition of CaCl₂ and ascorbic acid. Dried onion was subjected to compression and relaxation tests in Universal Strength Machine ZWICK 1445. The results obtained showed the mechanical properties of dried onion to largely depend on pretreatment before convective drying. Soaking onions in water and dipping in starch gruel with or without CaCl₂ resulted in increased elasticity and lower deformability. Addition of ascorbic acid levelled the stiffening effect of starch, while osmotic dehydration before convective drying produced „soft" dried material, susceptible to deformation.