The thermal sterilization is limited to use for fungi and bacteria in some kinds of dry powdered foods because of the heat sensitivity of their flavor. The sterilization method using impulsive loads or shock waves has the characteristic to sterilize foods without heating. Higher shock pressure can shows higher disinfecting action, but has some problems such as the degradation of foods and the hardness of handling. The proper choice of energy sources is one of points to make the method push to the industrial level. Safety and facility are also important factors to develop the practical system. In this paper as the case of the lowest limit of the impact load, the powder was impacted by mechanical hammer. It was found that the iterative impacts showed the disinfecting effect although the efficiency was low at an impact. Several processing cycles were required to show the significant decreasing of bacteria, because the apparent colony number (not actual bacteria number) increased in the impact process. The numerical model to estimate the mechanical condition in sterilizing process is also presented in this paper.