Mathematical models to describe thin-layer drying and to determine drying rate of whole bananas

Banana is a fruit produced in most tropical countries. According to the literature, the post-harvest loss is about 40% of the production. To reduce the losses, an alternative is to dry the product. In this context, the main objective of this article was to describe the thin-layer drying of whole bananas. To describe the convective drying process, a mathematical model is normally used. In this article, several empirical models were selected to simulate experiments of thin layer drying accomplished with whole bananas at temperatures of 40, 50, 60 and 70 °C. In the selection, it was imposed that mathematical expressions must be obtained from each model to calculate the drying rate and also the process time. The process time ranged from 1200 (70 °C) up to 3265 (40 °C) min. The maximum drying rate occurs at the beginning of the process and varied between 1.95 · 10^-3 (40 °C) and 3.60 · 10^-3 (70 °C) min^-1. The statistical indicators (determination coefficient and chi-square) showed that Page and Silva et alii models were the best ones to describe the drying kinetics. These two empirical equations enable to write mathematical expressions for the drying rate and process time, and these expressions produced results which can be considered equivalent.