But the bacteria will start to multiply again if the temperature is allowed to rise during storage. It is therefore important to keep the milk well chilled. Farm cooling equipment Spray or immersion coolers are used on farms which deliver milk to the dairy in cans. In the spray cooler, circulating chilled water is sprayed on the outsides of the cans to keep the milk cool. The immersion cooler consists of a coil which is lowered into the can.
Chilled water is circulated through the coil to keep the milk at the required temperature.
Where milking machines are used, the milk is collected in special farm tanks. These come in a variety of sizes with built-in cooling equipment designed to guarantee chilling to a specified temperature within a specified time. These tanks are also often equipped for automatic cleaning to ensure a uniformly high standard of hygiene. In former times milk was delivered to the dairy twice a day, morning and evening. In those days the dairy was close to the farm.