engleski

Effect of cultivation and drying temperature on rehydration ability of the carrots and potatoes

Drying is one of the most favourable preservation techniques of agricultural products. Water that is removed from a plant tissue during dehydration cannot be replaced in the same way when the tissue is rehydrated, because some of the changes cosed by drying are irreversible. The loss of cellular osmotic pressure, changes in cell membrane permeability, solute migration, crystallisation of polysaccharides, reduces of starch hydration degree and coagulation of cellular proteins all contribute to texture changes. The rate and extent of rehydration may be used as an indicator of dried product quality. Those plants that are dried under optimum conditions suffer less damage and rehydrate more rapidly and completely than poorly dried ones. A comparative study of the influence of cultivation and drying temperature on water uptake of dried carrot and potatoe pieces during soaking was conducted. Carrot and potato that have been grown under varied conditions (conventional, ecological) were fluid-bed dried on different temperatures (60, 70, 80, 90 °C) and then rehydrated. Obtained results were compared and statistically processed in order to assess the effect of factors and their possible interaction. Statistical analysis showed that cultivation has no effect on rehydration ability, while drying temperature has a significant influence on water uptake of both vegetables. With a drying temperature increase the final moisture content after rehydration decreases. Interaction between two examined parameters on carrot rehyration was observed, which indicated that drying temperature had different influences on conventional and ecological cultivated carrot. After two hours of soaking, carrot absorbed 58-82% of water while potato absorbed 37– 59% water that was removed by drying. The smaller amount of absorbed water could be the consequence of the higher starch content and extensive textural damages during potato drying.

fluid-bed drying; rehydration; carrot; potato

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