A tunnel pasteurizer having a tunnel, through which the material to be pasteurized is conducted and sprayed or sprinkled with water, and with a trap region for the draining water arranged on the bottom of the tunnel, pasteurizer and a plurality of temperature zones arranged in the transport direction, and the trap region is divided into separate trap zones which correspond to the temperature zones, from which the water is re-supplied to the respective tunnel zones, and comprising a control means for controlling the water temperature in the temperature zones. To improve control of the temperature in the individual temperature zones, the control and the tubing of the trap zones is adapted such that water can selectively be taken from the individual trap zones for temperature control and can selectively be returned to other temperature zones, wherein water is buffered in the individual temperature zones separate from other temperature zones in a respective zone buffer.