We studied the microstructural changes in freeze dried carrots due to water vapour sorption, including
the influence of different drying treatments. Small cylindrical freeze dried samples were stored for
prolonged time in a desiccator at 22 °C and 100% relative humidity. The moisture uptake was quantified
by weighing. The microstructure was visualised by X-ray microtomography (µCT) using a SkyScan 1172
bench-top system and also the facilities of the ID19 beam-line of the European Synchrotron Radiation
Facility (ESRF) in Grenoble. Morphological changes caused by water sorption were examined by imaging
the samples at different times. High resolution Synchrotron µCT images revealed the swelling of the pore
walls. The diffusion of water vapour into freeze dried carrots is slow. It takes about 15 days to reach
equilibrium. Within 1 day, sorption of water resulted in swelling of the pore walls. After longer sorption
times large pores remain unhydrated. The water uptake results in shrinkage of the samples which can be
attributed to viscoelastic relaxation. No significant differences were observed between different drying
treatments.