Comparing the water absorption capacity of the materials under study, it can be observed that the one prepared with cassava starch absorbs 64% and gradually reduces its capacity by 60% reaching a final value of 27% when the dose applied to the starch increases until 50 kGy. The plastic prepared with bean starch has a lower water absorption capacity (47%) that decreases near 30% as a consequence of the starch irradiation to a final value of 32%, as can be seen in Fig. 1. In this last case, no further variation is noticed as the applied dose increases. This behavior might be explained as a consequence of more radiolytic products being produced in the case of the amylopectin-rich cassava starch thus generating more branching points in the starch–protein matrix, and also because of the smaller dimensions of the radiation generated species.