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 continuous slot (28) is formed in the roof (8) of the tunnel and extends from the entrance (18) to the exit (20). Poultry suspension shackles (24) are able to pass through the slot (28). Thus, poultry carcasses are able to be conveyed through the tunnel (2). The slot (28) follows a path which reverses direction at least once. Typically, the slot (28) is generally S-shaped.
