Study of drying and rehydration kinetics of carrot cylinders

Abstract

Product drying is the most popular method of product preservation in the food industry, while rehydration is a process that results in restoration of the properties of the product. During the carried out study characteristics of drying and rehydration were examined. The aim of this study was to investigate drying and rehydration characteristics and experimentally determine the changes of sample dimensions of carrot cylinders during drying and rehydration processes. Cylindrical carrot samples of 10 mm and 15 mm diameter were cut using stainless steel die. Prior to rehydration the samples were dried in a convective oven at temperature 40 ºC for 24 hours in laboratory conditions. Samples were weighed during the first 6 hours and at the end of the experiment. At specified time intervals the diameter and shrinkage were examined. The dried carrot samples were then rehydrated in a water bath at temperature 23 ºC for 24 hours. The weight of the samples was examined at specified time intervals over the first 6 hours and additional measurement of a diameter and thickness at the end of the experiment was performed. Results of this study showed that thickness of carrot cylinders decreases 1.8 times during the drying process, but after the rehydration process the thickness size returns up to 93 %, while the diameter changes are smaller in both processes. As a result of drying, the diameter changes by 35 %, but after rehydration its size returns to 82 %. As a result of drying carrot samples lose 87 % of their weight for 24 hours, but after rehydration for the same time about 40 % of their initial weight returns. Besides, about 70 % of the recovered weight returns during the first 3 hours of rehydration. Results of this study can be used for modelling purposes of drying and rehydration characteristics of carrot cylinders.