On the Influence of Glass Transition on Shrinkage in Convective Drying of Fruits: A Case Study of Banana Drying

Abstract

The ideal shrinkage model assumes that the extent of shrinkage is equal to the volume of liquid water removed from the dried medium. Generally if a material undergoes glass transition during the drying process, shrinkage will no longer be ideal. The aim of this study was to observe how the glass transition temperature influences the shrinkage kinetics. Cylindrical banana samples were dried. Shrinkage extent was significant for all drying conditions (temperature: 30–50°C, relative humidity: 0–80%). Deviation from linearity was found to be affected not only by drying air temperature but also by its relative humidity.

Keywords:

• Desorption isotherm
• Drying flux
• First drying period
• Glass transition temperature

ACKNOWLEDGEMENTS

The authors acknowledge the State of São Paulo Research Foundation (FAPESP) for the Ph.D. scholarship granted to M. E. Katekawa (Process no. 01/14213-9) and also for the research grant (Process no. 00/08166-5), which allowed to purchase the DVS system.

Notes

^a Reference value.

^a Maximum error for X_m = 0.002.

^b Maximum error for k_G = 0.02.

^c Maximum error for C_G = 3.

Error in RH = 0.1%. Error in V/V_i = 0.005.