One of the most efficient ways to heat a large quantity of milk is with a coffee urn. Using a coffee urn, you can make 3 to 5 gallons of hot milk in 30 minutes. This is a great way to make hot chocolate or lattes for a large number of people such as at a church function, a school or corporate party. When heating milk in a coffee urn, you should pay careful attention to how the milk-warming process needs to be done. Without the proper steps you will end up with burnt milk that has the potential to curdle.
Pour 3 to 5 gallons of refrigerated cold milk into the urn while it is still turned off.
Plug the urn in. If the urn has a heat setting, place it on medium heat. If it doesn't have a heat setting, then use a thermometer to pay close attention to the temperature.
Stir the milk continuously with a large stirring spoon as it is heating. Failure to do so, will result in burnt milk because the heating element is on the bottom of the urn. If the milk sits on the heater for too long, it will burn it.
Watch the temperature with the thermometer until it reaches 160 degrees F. If you are serving children, you may want to serve the milk at a cooler temperature, such as 130 degrees F. Place the urn on warm to maintain the temperature.
Do not let your milk remain below 140 degrees F for more than 20 minutes as bacteria may grow. Overheating the milk can curdle it, potentially making people sick.