Investigation of shrinkage of cherry and sour cherry during drying

In this study, drying, rehydration and shrinkage of cherry and sour cherry grown in Sultandağı location of Afyonkarahisar province were investigated. Empirical drying models, given in literature for describing time dependence of the moisture ratio change, were fitted to experimental drying and rehydration data and model parameters in equations were determined by multiple regression analysis. The performance of models was evaluated using various statistical parameters such as t-test, chi-square ( ? 2), and the regression coefficient (R2). Drying characteristic of fresh and pretreatment fruits were investigated for four different temperatures in the temperature range of 45?75 oC. The shrinkage behaviors of both fruits were investigated during drying by measuring volumes and diameters of fruits in regular time interval. It was determined that drying of cherry and sour cherry, pretreated with 2 % Ethyl oleate and 5 % sodium hydroxyl and 2 % ethyl oleate and 5 % potassium carbonate, respectively, was faster than in the other experimental conditions. Diffusion coefficients were calculated for both shrinkage taken into consideration and not consideration, owing to drying of both fruits occurred as the first falling period in all drying temperature and pretreatments. The shrinkage results showed that diameter and volumes of cherry and sour cherry during drying decrease nearly 40 % and 80 % according to fresh fruits, respectively and shrinkage was increase with increasing temperature. The decrease in the volume of fruit was higher than the decrease in the weight of fruit while drying, therefore, an increase was seen in the density of the fruits. When pretreatment was negatively effected shrinkage behavior of cherry, the shrinkage of sour cherry was decrease with pretreatment. Henderson ? Pabis, Newton Model and Henderson ? Pabis, Logaritmic Model could be proposed respectively to evaluate the moisture ratio of cherry and sour cherry with drying time. The most important result of rehydration experiments can be given as efficiency of diffusion mechanism on moisture uptake, obtaining lower moisture diffusion coefficient in case of taking into consideration the change in fruits diameter and faster moisture uptake of dried fruits in high temperature.