How to Pasteurize Milk at Home
Pasteurizing Milk Takes Time but Avoids Problems Later
Reading Time: 5 minutes
Learning how to pasteurize milk at home is just one facet of owning dairy animals. A crucial one.
The call came straight from the USDA: “Call me back when you get this. We need to talk about your goat.”
I had adopted a sweet LaMancha and her six-day-old babies. The goat’s previous owner had died, and his niece wasn’t set up for caring for goats. I took them home and kept them separated from my other goats until test results came back.
A new goat owner, I needed assistance with the blood draw. The representative of the Nevada Goat Producers Association pointed to three check-boxes for the three big, bad goat diseases: CL, CAE, Johnes. “And if you intend to drink her milk,” she said, “I recommend testing for these as well.” Brucellosis: check. Q fever: check.
The goat tested positive for Q fever. And the results were so important that the state veterinarian called me personally.
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After a moment of panic, I explained my setup: I was a small-scale goat owner, not a business of any sort. But yes, I did intend to drink the milk. And he explained that my goat could have caught Q fever anywhere: it’s spread by ticks but it’s transmitted to humans and other goats mostly through placenta/fetal tissue and through milk. The primary symptom of Q fever in goats is abortions and/or low birthweight, failure-to-thrive offspring. Because this goat had come with two extremely healthy babies, he theorized that she had been treated for Q fever and the test had merely detected antibodies from an old case.
“…So, do I have to get rid of my goat?”
He chuckled. “No, you can keep your goat. But if you don’t already know, learn how to pasteurize milk.”
If you step into the shallowest depths of the homesteading world, you’ll hear outcries about raw milk benefits and why we shouldn’t have to pasteurize. And the truth is: raw milk has outstanding benefits if all is well with the animal. But many goat illnesses transmit through milk: brucellosis, Q fever, caseous lymphadenitis. A century ago, before refrigerated trucks brought milk from the countryside into urban areas, raw cow milk was a major vector of tuberculosis.
If your animal hasn’t been tested clean of all the diseases I listed above, I suggest you learn how to pasteurize milk. If you receive raw milk from someone who has not received a clean test of those diseases, learn how to pasteurize milk.
But avoiding diseases, though it’s the most important reason, isn’t the only reason to learn how to pasteurize milk. It extends the milk expiration date and it helps with dairy crafting projects.
One of my writers for Goat Journal had goat milk and freeze-dried cultures in hand, ready to make chèvre cheese. She followed the instructions perfectly except for one: The packet holding the cultures specifically said, “heat one gallon of pasteurized milk to 86 degrees F.” She had purchased the milk and followed the same food safety rules most home cooks learn: cool it, refrigerate it. After about four days in the refrigerator, she warmed and cultured the milk. The next day, it was still liquid and didn’t smell all that great. Something — it could have been anything, really — had contaminated that milk in those short days. Perhaps bacteria already existing in the milk, which wouldn’t have made humans sick but was plentiful enough that the cheesemaking cultures didn’t have room to grow.
By learning how to pasteurize milk, you gain more control over those beneficial microbes needed to make homemade yogurt, sour cream, or making goat cheese. I will even re-pasteurize my store bought milk if I’m about to add dairy cultures. Just in case.
How to Pasteurize Milk at Home:
Pasteurizing milk is this simple: Heat it to 161 degrees F for at least 15 seconds or to 145 degrees F for 30 minutes. And there are several easy ways to do this*:
Microwave: Though I wouldn’t recommend this method, it would kill pathogens if you topped 161 degrees F for the required 15 seconds. But it’s difficult to judge temperature and hot spots in microwaved food, meaning your milk may burn or not all areas may reach safe levels.
Slow Cooker: I use this method for my yogurt and chèvre to save on steps and dishes. Simply heat milk on low until hot enough. This should take 2-4 hours, depending on crock size and milk volume. It’s perfect for when I have three-hour meetings but still want to make cheese. I have never had scorched milk unless I use the high setting.
Stovetop: Advantages to this method: it’s quick and can be done in any pot that holds liquid. Caveats: it’s easy to scorch milk if you don’t pay careful attention and stir often. I use medium heat, but that means I must pay close attention. Any higher and I accidentally burn the milk.
Double Boiler: This follows the same concept as stovetop, but the extra water layer between pots keeps you from scorching the milk. If you have a double boiler, take advantage of it. You’ll save time and hassle.
Vat Pasteurizer: These are expensive, and a lot of households can’t pay that kind of money. Small farms running dairy operations may want to consider one, though. These use “low temperature pasteurization” to keep milk at 145 degrees F for 30 minutes then they rapidly cool the milk, which preserves flavor better than the higher temperatures do.
Other options: The steamer feature of a cappuccino machine effectively pasteurizes milk if it brings temperatures above 161 degrees F for over 15 seconds. Some people have even used their sous vide water bath units to pasteurize, since those devices are designed to reach and hold a specific temperature for a specific amount of time.
*If your state allows you to pasteurize and sell your animal’s milk outside of an inspected food establishment, you will probably be required to use a specific method such as a pasteurizing vat.
Chilling the Milk
When I make yogurt and chèvre, I turn off the slow cooker and let temperatures descend to necessary levels for culturing. But with those dairy products, I don’t mind a little “cooked” flavor because the probiotics and acidification add other flavors that mask the taste.
If you’re pasteurizing milk for drinking, consider flash-chilling it to preserve the best flavor. Just sticking the pot in a fridge or freezer sounds easy, but all that heat could raise the temperature and humidity in your fridge to unsafe levels. Steam condenses on freezer racks. I find the easiest way to chill milk fast is to put a lid on the pot, to avoid splashing water in the milk. Then set the milk in a sink full of ice water. I keep quite a few ice packs in my freezer for this purpose, to save on the amount of ice cubes I need to make or buy.
If you want to make cheese right away, let the milk cool to the temperature necessary for your specific cultures. Or cool it, pour into a sterilized container, and store the milk in your refrigerator.
Learning how to pasteurize milk at home is a critical part of a home dairy, whether you need to avoid a diagnosed or unknown disease, control the desired cultures within a cheese project, or extend milk’s expiration date for longer storage.
What is your favorite way to pasteurize milk? Let us know in the comments!