After they are killed, chickens pass through a warm water reservoir (50-60 °C; 122-140 °F) to facilitate easy feather removal. This is called scalding. The scald-tankis considered to be an important source of cross contamination between flocks. However, survival of Campylobacter and Salmonella in the scald tank is low. In order to minimise the risk, the process circumstances should carefully be observed.
To reduce cross contamination but also to improve the washing effect, the counter current principle is advised to use in this scald tank. Multi-phase scalding can be introduced when several tanks are placed next to each other. In order to reach an optimum result for picking the chicken, turbulence in the water can be created (e.g. by injecting air). The scalding-time depends of the water temperature.
The pasteurizing effect of a scalding tank is in balance with the influx of bacteria. This can be concluded from observations during scalding.
For hygienic purposes at the end of a production day the tank should be emptied and cleaned. After filling with water a good way to kill pathogens present in the tank is to increase the temperature till pasteurising temperature (>70C) and leave the water in till the next day.
A recently developed alternative for immersion scalding is the AeroScalder. The AS is entirely enclosed and consists of two chambers; an air conditioning chamber where the moisturized hot air is prepared and, next to it, the scalding chamber itself through which birds are conveyed and into which the scalding air is blown. Moisturized hot air is blown forcefully most difficult places of the broiler, preventing overscalding of fragile parts. It penetrates and separates the feather pack, transferring heat effectively to the feather follicle. Air temperature will depend on whether products are to be hard, medium or soft scalded. After having been blown over the birds, air is drawn back into the conditioning chamber and re-conditioned for re-circulation.
Precise temperature control ensures a perfectly scalded product in all situations.
Food safety issues: Cross-contamination in the scald tank(s) in spite of counter current flow of product and water.