Abstract
Modeling the thin-layer drying of foods is based on describing the moisture ratio versus time data by using a suitable mathematical model or models. Several models were proposed for this purpose and almost all studies were related to the application of these models to the data, a comparison and selecting the best-fitted model. A careful inspection of the existing drying data in literature revealed that there are only a limited number of curves and, therefore, the use of some models, especially the complex ones and the ones that require a transformation of the data, should be avoided. These were listed based on evidence with the use of both synthetic and published drying data. Moreover, the use of some models were encouraged, again based on evidence. Eventually, some suggestions were given to the researchers who plan to use mathematical models for their drying studies. These will help to reduce the time of the analyses and will also avoid the arbitrary usage of the models.
Highlights
One common method to preserve food and agricultural products is drying, in which, moisture is removed by evaporation and simultaneous heat and mass transfer takes place between the sample and the adjacent environment [1,2]
A careful inspection of the drying data available in literature suggested that the number of drying curves is limited and, in general, can be divided into four categories that are simulated in Figure 1: (i) concave curves, which are simple exponential decaying curves (Figure 1a); (ii) strong tailing curves, which are similar to concave curves, though their initial period is much steeper (Figure 1b); (iii) sigmoid-type I or slightly convex followed by concave curves (Figure 1c); and (iv) sigmoid-type II or concave followed by slight convex curves (Figure 1d)
This study reviewed some of the thin-layer drying models that are commonly used to describe the drying kinetics of different foods
Summary
One common method to preserve food and agricultural products is drying, in which, moisture is removed by evaporation and simultaneous heat and mass transfer takes place between the sample and the adjacent environment [1,2]. Parameters of theoretical models have physical meaning because they are based on the general theory of heat and mass transfer laws, and they take into account the fundamentals of the drying process. These models can be used to explain the phenomena occurring during drying. The comparisons of the models were based on fitting performances, which were generally the coefficient of determination (R2 ), and uncertainties (standard error or confidence interval) of the model parameters were rarely given together with the parameter values They are as important as the parameter values themselves, and parameter estimates are uninterpretable if the uncertainties are omitted [17]. Thin-layer models were classified as theoretical, semi-empirical and empirical, no classification will be performed in this review, and we will examine the models without considering their background
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
