Unless you’ve lived on a farm or a dairy, you’ve probably never needed to know how to pasteurize your own milk. You may not even know exactly what pasteurization is. Created by Louis Pasteur, this process of heating liquid to a high temperature works to kill bacteria and inactivate some of the enzymes that cause milk to spoil without dramatically changing the flavor, appearance or nutritional value. The USDA warns that drinking unpasteurized milk can result in illness and unless you seek raw milk, the product sold in grocery stores has been pasteurized to prevent the spread of disease and to extend its storage life. Still, in the spirit of “better safe than sorry,” you can pasteurize milk at home using one of the methods below.
To pasteurize milk at home, you’ll need:
- Raw milk
- A refrigerator that’s set between 35º-40ºF
- A large pan or sink
- A double boiler pan
- A candy thermometer
- A spoon
- If you plan to pasteurize milk at home frequently, you’ll want to invest in a home pasteurization machine. According to an article published by South Dakota State University’s College of Agricultural & Biological Sciences, a home pasteurization machine is the preferred way to pasteurize milk at home. It can safely treat both large and small quantities of milk in a short amount of time. Home pasteurization machines are available at dairies or farm supply stores and online. However, unless you plan to pasteurize milk regularly, this unit may be prohibitively expensive.
- If you don’t have access to a home pasteurization machine, there are two methods that can be used. First, milk is brought to a high temperature for a short period of time. Second, a slightly lower temperature is maintained for a longer period of time. For both methods, be sure to assemble your tools in advance. Sanitize all of your utensils, along with the containers in which you plan to store your milk, by plunging each item into water that is between 175º and 190ºF. Prepare a sink or a large container for your cold water bath and be sure you have ice on hand.
- The “continuous high-temperature short-time” method is the more reliable way to pasteurize milk at home without a machine. Boil water in the bottom of a double boiler pan and in the top, heat milk to 165°F. Maintain this temperature for fifteen seconds, stirring constantly. While stirring, remove the pan from the stove and set it into a sink or container of cold water to cool the milk immediately to 145°F. Add ice to the water to get the milk colder, stirring occasionally, until the temperature falls below 40°F. Store the cooled milk in clean, covered containers in a refrigerator set between 35ºF and 40°F.
- The batch method is sometimes used to pasteurize milk at home. However, according to Michigan State University, it’s considered less preferable than the continuous method because temperature is critical. In a large pot, bring water to 150°F. Put the milk into sterilized jars and then immerse them in the hot water for 30 minutes. It’s crucial to maintain a water temperature of 150°F for 30 full minutes. If it drops below 145°F at any time, the process must be restarted. It’s also important that all tools, including stirrers, thermometers and any other utensils, stay in the milk until it has been completely cooled to prevent contamination. After the milk has been held at 150°F for 30 minutes, use tongs to transfer the jars to a cold water bath and cool the milk to 40°F, adding ice if necessary. Store the jars in a refrigerator set between 35ºF and 40°F.
- Do not use the microwave to pasteurize milk at home. Microwave ovens generate uneven heat, so they are not a reliable or effect way to pasteurize raw milk.