I’ve recently come across a lot of information and misinformation about canning butter at home. Because of the level of controversy, and the amount of unsafe advice out there, I wanted to set a few things straight.
If you’ve read any of the articles or blog posts out there, then you probably already know that the USDA does not recommend canning butter at home. The reasons stated are many, and there is an abundance of misinterpretation of the statements made by the USDA, even by those who directly quote it. Let’s clear this up first: the USDA does not have a recommended procedure for canning butter at home. This is not because they have ulterior motives. It is simply because they have not created and tested a procedure which they can reliably claim to be safe. And if they can’t reliably claim a procedure to be safe, then they won’t recommend it.
This may lead you to ask why the USDA has not done the legwork to create and test such a procedure. On this, I can only speculate. Perhaps it is because of a lack of funding to the department(s) responsible. Perhaps they have in fact spent countless hours in development and have discovered that with the equipment available to the home canner, such a procedure is not possible. Again, I can only speculate on their reasoning, and such speculation distracts us from actual facts.
Now that we have the USDA part out of the way, let’s talk about what butter actually is. Even though I know better, I still find myself constantly surprised at how little people know about butter. It’s constantly referred to as a fat, which is understandable, since fat does make up the bulk of butter’s composition. However, “whole butter” is not 100% fat. It is in fact an emulsion of fat, water, milk solids, and sometimes salt. Depending on who made the butter, usually butterfat makes up somewhere between 80-85% of “whole butter”. American butter tends to have less fat, European butter tends to have more. Milk solids and any salt usually comprises around 1-2%, while the rest is water.
When all of the water and milk solids have been removed, the resulting product is called “clarified butter”. Notice that I didn’t mention salt in this equation. This is just conjecture, but I’m not entirely convinced that clarfying butter will remove 100% of the salt content from salted whole butter. This is irrelevent to me, since I only buy unsalted whole butter (not counting butter spreads), but it may be relevant to you.
Now that we know more about the composition of butter, it’s time to talk about the methods presented for the preservation of butter at home, and why they should concern you.
When you can food at home, you should sanitize the jars that you use, as close as possible to the time that you use them. You should wash them in warm, soapy water and rinse them, at the absolute least. If I were you, I would take it one step further and run your jars through the dishwasher, and let them sit there, with the door closed, until you need them. There are other methods which are suitable, all of which involve steam, but the dishwasher is my preferred method.
What you should never do is heat your jars in the oven. Mason jars are not designed to be heated in the oven, and doing so increases their chance of breakage. The dry heat of the oven also does not adequately sanitize jars. I read one blog post that recommended oven heating jars, on the basis that water inside the jars is undesirable. Remember that butter already has water in it; the residual from sanitizing jars using a wet method will not suddenly contaminate the fat by being water.
With jar sanitation out of the way, we are free to contemplate the actual canning method. According to the USDA, there are plenty of sites that will recommend melted butter into jars and closing them, with no further processing. Somehow I managed to miss any of these sites. Nevertheless, as the USDA tells you, this method is completely unacceptable. Just storing something in a jar is not the same as canning it, and this method does not meet any definition of canning.
One might consider steam-canning as their method of preservation. According to the USDA, the only thing you should ever steam can is juice. Personally, I won’t even do that. As far as I’m concerned, the only thing that steam canners are useful for is sanitizing jars. And as I’ve already said, I don’t even use them for that. If you have one, just throw it away.
Next up is boiling water canning. I did see a number of blogs recommend water bath canning, which is disconcerting to me. Let’s be clear: boiling water canning is only acceptable for high-acid foods. This means that any food with a pH above 4.6 should never be processed in a boiling water canner. Since butter is in the 6.1 to 6.4 range, it should never be processed in a boiling water canner.
Now, wait. What’s the deal with acidity? There are a number of factors which affect the safety of food. It’s easy to remember them with the abbreviation FAT TOM: fat, acidity, time, temperature, oxygen, moisture. These all play a role in canning, though fat is actually the one that I’m the least concerned with.
There are a number of food-borne illnesses that plague our society, but by far the worse one in relation to canning is a bacteria called clostridium botulinum, which is responsible for an illness known as botulism. These bacteria love moist, low-oxygen, low-acidity environments. They are also very heat stable: when they encounter environments that are too hot, they protect themselves with an outer layer called a spore, which can withstand temperatures up to 240F. Because water boils at 212F at sea level (and less above sea level), a boiling water canner cannot destroy these spores.
This is also disconcerting since one of the important functions of canning is to remove oxygen (though not all of it) from the jars. Because clostridium botulinum loves low-oxygen environments, and it loves moisture (which is always present in canned foods), canned food would normally be a haven for this bacteria! But it cannot thrive in acidic environments. The higher the acidity (meaning the lower the pH), the less comfortable this bacteria is. A pH as low as 4.6 is enough to disable it. This is why pickles, jams, jellies, and fruits can be canned using boiling water: they all involve an environment where the acidity is high enough to disable the growth of clostridium botulinum.
Our last option for canning is a pressure canner, which as you’ve probably guessed by now, is the only acceptable method of canning low-acid foods. Meats and vegetables are all considered low-acid foods, as is butter. This tells you that if you ever come across a procedure for canning butter that does not involve a pressure canner, it cannot be considered safe, and you should move along.
However, just because a procedure involves a pressure canner, doesn’t mean it is safe. Let’s talk about how pressure canners work, and how this relates to butter.
As I said before, water boils at 212F. It also freezes at 32F. Going back to junior high chemistry, we know that matter has three states of being: solid, liquid, gas. Well, okay, technically there are four, the last being plasma. Water below 32F is in a solid state, water between 32F and 212F (at sea level) is in a liquid state, and water above 212F (at sea level) is in a gaseous state. And for those interested, water enters a plasma state at around 12,000 degrees K.
Low-acid, low-oxygen foods are a perfect breeding ground for clostridium botulinum. Our only defense against this bacteria is heating it above 240F, which means we need to use water that is in a gaseous state (steam). A pressure canner filled to the brim with water doesn’t allow enough room for steam to grow, which is why we only add around 3 inches of water. Water inside the canning jars is also important, because as the water on the outside turns to steam, the pressure will also cause the water on the inside of the jars to turn to steam.
Once the steam inside the canner, and subsequently inside the jars, reaches 240F, the mass genocide of clostridium botulinum spores has begun. Temperature isn’t enough to kill those bacteria though; it also takes time. And just because the steam inside the canner has reached 240F, doesn’t mean all of the food inside the jar has reached that temperature. The thicker food is, the longer it takes to heat it thoroughly.
How does this relate to butter? Whole butter has moisture in it (close to 20%), which creates an environment inside the jar that can be used to heat the food with it to 240F. This should tell you that clarified butter is probably not a safe candidate for canning. I say probably, because I don’t know for sure.
In fact, this is where fact begins to fail us, because we don’t yet have all of the facts. Whole butter is likely a better candidate for canning than clarified, because of the moisture content, but there’s still a matter of time to be considered. Does it require 25 minutes like beef broth? 90 minutes as with chicken? 100 minutes like for certain fish? Perhaps the number is lower than 25 minutes, or higher than 100 minutes? This is the thing that we don’t know. Perhaps it needs to be canned at a pressure that is unsafe or impossible using a home pressure canner.
Now of course you could run a number of tests yourself. You will need a lot of butter, a lot of time (months, as you continue to test the long-term safety of the canned butter), and of course some very expensive equipment to perform the testing.
In the end, it’s entirely up to you whether you decide to can your own butter. It’s also up to you whether you want to do any number of things which involve questionable safety. Are you willing to trust your life, and your family’s life to your procedure? Plenty of preppers are happy to do exactly that. Until I hear further word, I think I’ll just go without canned butter.