A pilot-scale process for continuous in-flow microwave processing of particulate pumpable foods, designed and implemented at RISE Research Institute of Sweden [1], was studied for heat treatment of a particulate, viscous model food at high temperature conditions at 2450 MHz. In this paper, the technology will be discussed as an alternative high-temperature short-time (HTST) processing method for a high-concentrated particulate model product. The technology combines TM 020 and TM 120 microwave mode heating. The rapidness in heating the product will be illustrated for selected time-temperature conditions after tubular microwave heating. The latter corresponds to the required microbiological inactivation, for a product intended for storage at ambient conditions or cool storage, respectively. As will be exemplified, the microwave HTST system studied results in large process flexibility. Additionally, it offers advantages in product quality.