A heat-treatment device for heat treating packaged products that are available in bulk, and to a method of using the device. The device includes: a chamber; a tank for containing a fluid of a density such that the packaged products float when they are poured in bulk into the fluid, the tank presenting an evacuation compartment for evacuating floating products, the evacuation compartment including a hatch that is suitable for being submerged and then opened so as to evacuate a portion of the fluid including the floating products; fluid supply means for filling the tank and for regulating the level of fluid in the tank; submersion means; recovery means; and reception means.