A mathematical model was developed to determine the sterility efficiency of a continuous high‐temperature/short‐time sterilizer for a liquid medium containing suspended particles of potato. A steam injection heating system, which is frequently used in industrial sterilization, was considered. Unsteady state balanced energy equations of the liquid medium and of the particles in the holding section and the cooling section were used to calculate the temperature distribution in the liquid medium, and also the particles as a function of time and inside position of the particle. The degree of sterility by the high temperature for the liquid medium and the particles was also calculated. It is shown that as the liquid medium achieved 16 orders of degree of sterility while in the holding section, the degree of sterility in the core of the potato is only 4 orders, which is far below the requirement. This phenomenon may cause a serious problem in the fermentation process. The results show that the cooling section predominates the sterility of particles. The degree of sterility for different potato sizes was also calculated. To meet the sterility requirement, increasing the residence time in the process or the sterilization temperature is required.