A scanning electron microscope (SEM) was used to study the morphology of starch granules and the strength of market Udon (Japanese noodles), that is, fresh Udon, frozen Udon and cooled Udon after cooking. Udon samples were cooked for a given time and observed with SEM and also we measured the breaking strength. The following results were obtained. 1.The degree of swelling of starch granules in cooked Udon samples differed with the position from the surface. The starch granules near the surface swelled extremely and did not retain their original granular form. 2.A black ring was observed in the cross-section of all cooked Udon in SEM images. The black ring may be caused by the difference in the water content between near the surface and the core of cooked Udon. 3.The starch granules in the core of cooked Udon had a distinct form, but they were not a round shape. The shallow surface layer of each starch granule swelled and gave high contrast. The core of the each starch granule showed low contrast because of its compact structure, which looked black in the SEM images. The area of the black zone was different among Udon samples. 4.There was a correlation between the total area of low contrast zone in the starch granules and the breaking strength of Udon. The area of low contrast zone can be used for an evaluation scale of cooked Udon.
