Rice crackers have been used to test masticatory ability, for mastication training, and investigate the dynamics of mastication in humans. However, no study has examined the relationship between the change in rice cracker structure during mastication and their physical properties in the food bolus, so the aim of this study is to investigate this relationship. In this study, artificial food boluses of 10 different rice crackers, each with a different texture and perceived ease of swallowing, were prepared using a bead mill. At each mastication stage (5-20 s), the permeation of saliva into the artificial food bolus and the status of particle shape were visualized by X-ray computed tomography, and physical properties were measured with a texture analyzer. By freeze-dr ying, it was possible to visualize inner structure of the artificial food bolus that stopped the enzymatic reaction and saliva absorption during each mastication stage. There were three types of artificial food bolus and positive correlation between swallowability and cohesiveness. Our results showed that rice crackers are easy to swallow if they are softened by quick permeation of saliva in the late stage of mastication, or remain until the late stage of mastication as pieces covered with digested starch.