Last week I wrote about Ellie having brought us four gallons of milk from her Jersey cow. After having done some research, I just wasn’t comfortable using it raw. While the risk of food poisoning with pathogens that could be in the milk itself (less likely) or come from equipment or fecal contamination during or after the milking process (more common) is low, it’s not zero. The consequences of food poisoning, especially with listeria, can be devastating. Pasteurizing milk and thus rendering it safe reduces the risk substantially. And it’s easy to do. Here’s how:
1. Note that pasteurized milk tastes best if it is cooled as quickly as possible after pasteurization. Accordingly, it is easier to work with small batches of 1 gallon or less. Also note that while the Oregon State University Cooperative Extension states that milk can be safely pasteurized in a microwave, most other sources, including the Canadians, assert that this is not true.
2. Decide which method to use based on your intended use(s) for the milk.
The USDA has established two safe ways for pasteurizing milk:
High Temperature Short Time (HTST)
Recommended for fresh usage—drinking, ice cream, etc., as it is faster and affects taste and color less.
Bring the temperature to 161°F (or 162°F/72°C if you live in Canada) and keep it at or above this temperature for 15 seconds.
Remove immediately from heat and plunge it into the ice bath. Replace ice and water as necessary to continue cooling the milk. Once it has reached 40°F, it can be refrigerated in sanitized containers. If it does not reach 40°F within 4 hours, it may have become recontaminated and must be pasteurized again.
Low Temperature Long Time (LTLT)
Recommended for cheese-making to avoid accidental overheating
Bring the temperature to 145°F (or 150°F/63°C if you live in Canada) and keep it at or just above this temperature for 30 minutes. Restart the timing if the temperature dips below 145°F.
Remove immediately from heat.
3. Pour the milk into a large double boiler. (Using a double boiler is critical to reduce the risk of scorching or burning. Improvise a large double boiler with an Instapot pot inside an extra-large stock pot. Use a cake cooling rack to elevate the inner pot off the bottom of the stock pot.) Set the temperature to medium-high. Use a candy or cheese thermometer to monitor the temperature of the milk. Be sure the thermometer does not touch the bottom or sides of the pan. Stir the milk and check the temperature frequently. As the milk approaches the desired temperature, stir it constantly to prevent hot and cold spots from developing.
4. Meanwhile, clean and sanitize heat-proof containers. Wash with soap and water and then sanitize with water that is at least 170°F for 60 seconds. Let air dry. Drying with a towel may re-introduce bacteria.
5. Create an ice bath to cool the milk quickly. Set the pot of pasteurized milk in the ice bath immediately. Stirring frequently helps remove heat faster. Change the bath water as needed to cool the milk as quickly as possible.
6. As soon as the milk reaches 40°F, cover and refrigerate. It should be good for 7-10 days. Pasteurization kills 90-99% of bacteria.
References:
https://extension.oregonstate.edu/food/preservation/home-pasteurization-raw-milk
https://vetmed.tamu.edu/news/pet-talk/home-milk-pasteurization/
https://myhealth.alberta.ca/Alberta/Pages/how-to-pasteurize-milk.aspx
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