engleski

Celery Root Drying in Fluid Bed Drier

The drying characteristics of celery root (Apium graveoleus var. rapaceum) were investigated using a bench-scale fuidized bed drier at different temperatures and different pre-treatments. Celery root was cut into rectangle-shaped samples 20x20x5 mm in size. Temperatures of fluidisation for non-treated samples have varied from 60 &ordm ; ; ; C to 80 &ordm ; ; ; C at airflow velocities of 3.50 m/s. Before drying at 80 &ordm ; ; ; C, samples were pre-treated either thermally or chemically, or both (blanching in hot water, dipping in 1% ascorbic acid solution, blanching in boiling 2% CaCI_2 solution, dipping in 2, 5% starch solution). The aim was to obtain celery root with approximately 7% water content, with good texture, rehydration capability and colour quality. The effect of temperatures and pre-treatments on the quality of dried celery root samples was determined on the basis of colour and volume changes and reconstitution characteristics. Kinetic equations were estimated using exponential mathematical model. The results of the estimation have exhibited correspondence to experimental results. As a result of drying of non-treated celery root at higher temperatures, drying time shortens, while rehydration properties improve. On the other hand, with the increase of the drying temperature, overall colour changes (DE) of non-treated samples increase. The bests results (short drying time, good rehydration properties and colour) were obtained when samples were pre-treatment with blanching (85 &ordm ; ; ; C for 3 min.), as well as with 2, 5 % starch solution (40&ordm ; ; ; C during 5 min.) and then dried at 80 &ordm ; ; ; C. Celery root pre-treated with boiling 2% CaCl_2 solution, has resulted in faster drying, but poor colour and rehydration ratio. Pre-treatment with 1% ascorbic acid solution has given poor results in general at drying temperature of 80 &ordm ; ; ; C. The observed differences in the drying kinetics should be considered when selecting the best drying conditions in order to improve the final product quality.

fluid bed drying celery root; blanching; rehydration

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