A water chiller involves a pre-cooling step where a countercurrent of cold water is used to lower the temperature of the carcasses. The carcasses are then fed into a chiller, a large tank specifically designed to carry the carcasses through in a given time.
An air chiller cools the temperature of the carcasses. By using controlled flows of cool air, the temperature can be controlled. No water is used in this method.
Air cooling can only be used when processing fresh products.