Koji making was carried out using buckwheat grits showed no growth of koji mold on the surface of the buckwheat testa. The explanation for this was that the growth of the mold was inhibited by a defensive mechanism against the mold by the plant and the structure of buckwheat testa. To investigate this, confirmation of the inhibitor and defensive mechanisms of the cuticular layer and lignin to the mold was performed. These experiments proved that the buckwheat testa did not have an inhibiting,

more »

... fensive mechanism in the cuticular layer and lignin to the mold. Furthermore, the surface structure of the buckwheat testa was determined by scanning electron microscope analysis. The result showed that the absence of a gap in the surface structure of the buckwheat testa, in contrast to the surface structure of other raw materials such as rice and barley; the structure was not attacked by the enzymes from the koji mold. From these results, it was suggested that the growth of the mold was inhibited due to these complex structures of the buckwheat testa.