Mould normally forms due to a lack of heat / ventilation. In this case it sounds as if the room is warm and the tiles are cold and condensation is forming on the tiles.
Wash the mould away wiith a solution of bleach and water.
Next see if it is possible to keep a more even temperature in he room - additional insulation?
Extract damp air:- Perhaps get a small electric extract fan installed within the glass of a window in that room.
The above should resolve the issue as long as you use the fan esp when cooking!
Maurice
January 2011