comparative study of the 35ºc sorption isotherms of cork stripped from the tree in 1968 and 2006

A study was made of the hygroscopicity of two samples of cork with the same characteristics, taken from trees of the same age but with a 38-year gap between debarking. This was achieved by plotting the 35ºC sorption-desorption isotherms and fitting them using the GAB model. Infrared spectra were used to determine any chemical changes in the cell wall. Extended exposure to controlled relative humidity and temperature did not cause hygroscopic changes to the cork. The equilibrium moisture content values were not significantly different in the two samples, but the monolayer saturation moisture content values were significantly lower in the older cork. This may be due to partial saturation of the moisture sorptive sites in the cell wall over time.