The invention relates to a method and an apparatus (2) for reducing the microbial count in particulate bulk material, in particular herbs and spices and other particulate foodstuffs, by treating batches of the bulk material with hot steam. In order to make better use of the thermal energy contained in the steam, the invention proposes that the bulk material is in each case alternately treated with steam in two separate chambers (6, 8), and that, after treatment of the bulk material in a chamber (6 or 8), some of the steam which is supplied to this chamber (6 or 8) is introduced into the other chamber (8 or 6) in order to preheat the still untreated bulk material in said other chamber (8 or 6).