Abstract: In order to explore the drying regularity of red dates and provide a theoretical foundation for the drying of red dates, the drying characteristics of red dates were evaluated in a laboratory scale dryer. The drying experiments were carried out at 50, 60 ℃ and 70 ℃ at a constant air velocity. Seven commonly used thin-layer drying mathematical models were selected and used to fit the experimental data using non-linear regression analysis for establishing a suitable mathematical model that describes the drying of red dates. The results indicated that the drying process involved two stages, acceleration phase and deceleration phase, without a constant-rate phase. The performance of different drying models was investigated by comparing their coefficients (R2), chi-square values (χ2) and root mean square errors (RMSE). Among these models, the Page model was the most suitable model for describing the drying curve of red dates with a R2 of 0.99921, χ2 of 0.0088687 and RMSE of 0.0082514. The effect of drying air temperature on the rate constant and coefficient of the Page model was also explored. Therefore, this model can adequately describe the change regulation of water content according to the comparison of experimental values and predicted values.

Key words: Ziziphus jujuba Mill, thin-layer drying, drying characteristics, mathematical model