Realtime monitoring of internal morphology of gel samples during drying process by X-ray computing tomography image using synchrotron radiation

Abstract

Abstract This study was conducted to evaluate the change in the internal morphology of a wheat-based gel sample subjected to a drying process using X-ray computed tomography (CT) imaging with synchrotron radiation. To monitor the process in real time, the instrument was equipped with a developed drying system. The water contents of the sample decreased from around 0.42 to 0.1 g-water/g-dry solid and the falling rate drying was observed in the 0–180 min of drying period. The mechanical properties of the gel sample, represented by the Young’s modulus, increased exponentially during the drying period. Thus, when subjected to low-water-content conditions, the hardness of the gel progressed sufficiently. In the X-ray CT images, small voids were generated uniformly in the sample during the early drying process, and the total number of voids and their volume also increased. Finally, they formed a band-like structure at the center of the sample. The total number of voids decreased at a rate of increase with the confluence of voids, and eventually reached a plateau. These results suggest that voids may be connected and cracked during drying. It was found that the drying process of a gel sample in this study proceeds in two phases: a void growth phase up to 60–80 min and thereafter, a crack generation phase. Consequently, the internal morphology of the gel was visualized using synchrotron-based X-ray CT imaging in real time, and it was demonstrated that the method is very effective for monitoring a gel during the drying process.