Shrinkage of cane (Arundo donax) II. Effect of drying condition on the intensity of cell collapse

To improve the drying method in the manufacture of woodwind reeds, green canes (Arundo donax L.) were dried under various humidity–temperature conditions and the intensity of cell collapse was evaluated from the swelling due to steaming during the recovery of collapse. At 30°C, the intensity of collapse was increased by slower drying. It was considered that: (1) slower drying resulted in higher sample temperature in the early stage of drying and acted to increase the collapse; (2) rapid drying stiffened the surface of the sample and such a shell prohibited the following collapse; (3) slower drying i.e., longer loading of liquid tension caused more remarkable and/or frequent viscoelastic yields of cells. Consequently, the intensity of collapse increased when the cane was dried from its waxy outer surface or in the presence of node: both of them retarded drying. On the other hand, higher drying temperature caused greater intensity of collapse in spite of faster drying. It was suggested that the thermal softening of cane cells leads to easier yielding of the cell wall, and at the same time the rapid drying does not allow the recovery of collapse after the disappearance of free water. These results indicated that faster drying at lower temperature is preferable for drying cane with less collapse.