Influence of ripeness and air temperature on changes in banana texture during drying

This study aims to characterize how the rheological properties of slices of Cavendish Grande name bananas change during the hot air drying process. Since the degree of ripeness of fresh banana considerably affects the rheological properties of the dried product, changes in fresh banana were first of all monitored during storage at room temperature and humidity. This study made it possible to determine the parameters which discriminated between degrees of fruit ripeness-moisture content, sugar content in the pulp, firmness of the banana with peel (S) and peel color (a*). Two non-linear regression correlations linked S and a* to storage time. Glucose content was correlated with the values of S, a* and moisture content in order to avoid this measurement very time consuming. Secondly, the changes in rheological properties were monitored by penetrometry throughout the drying experiments. This study showed that a radical change in the rheological behavior of the slices occurred depending on the fruit ripeness after 4, 6 or 8 h of drying at 80 degreesC: they lost their deformability and became brittle. An analysis of the thermo-mechanical properties of the slices by dynamic mechanical thermal analysis showed that this abrupt change in the properties must be related to the product going below the glass transition temperature (T-g) as it is cooled after drying. (C) 2002 Elsevier Science Ltd. All rights reserved.