A tunnel (2) for the in-line anti-bacterial treatment of plucked poultry carcasses (or other animal carcasses) with a liquid cryogen or a cold gas at a temperature of less than 0°C has an entrance (18) and an exit (20) for the poultry carcasses. A monorail conveyor (22) extends from the entrance (18) to the exit (20) and passes thorough the tunnel (2). Poultry suspension shackles (24) are able to pass along the conveyor (22). Thus, poultry carcasses are able to be conveyed through the tunnel (2). The conveyor (22) may follow a path which reverses direction at least once.
