A novel tubular industrial apparatus for the surface pasteurization of particles has been studied. Particles are conveyed through a helical pipe by vibrations created by off-balance motors. The residence time of barley grains was characterized. The behaviour of the system was a function of motor angle and motor speed. The residence time could vary up to 21% during one experiment of 2 h (20, 740 rpm). However, ranges of processing conditions were identified that produce stable operation and thus effective pasteurization of product. In some cases, residence time increased by up to 7% of the initial value over consecutive experiments (40, 710 rpm). Some reasons for this phenomenon have been proposed and tested. The formation of a powder layer inside the pipe has been proven to affect the residence time of barley grains. A simple model for pasteurization of particles has been developed to characterise the impact of variation in residence time on microbial inactivation. (C) 2016 The Authors. Published by Elsevier Ltd.