We are conditioned to think that sour milk is a harmful thing. If you are talking about pasteurized milk, it can be. Sour pasteurized milk can have some really nasty opportunistic pathogens in it.

Raw milk, on the other hand, is a different thing entirely. When it sours, it develops a wide range of microbial growth, including many helpful probiotics. It DOES contain some bacteria and fungi that would be considered to be harmful pathogens when in higher concentrations, but they are balanced and neutralized by the much more plentiful helpful microbes.

So why is pasteurized milk so risky when it is soured?

If you kill all the good bacteria and yeasts, then the milk is completely lifeless – for all of about half a millisecond, until it comes in contact with air again (or the inside of a milk jug, sterilized or not, or equipment, etc). It becomes a fertile environment that happily cultures any opportunistic bacteria or fungi that come along – the fast growing nasties are able to thrive, breed, and multiply without restraint. There are no natural inhibiting “enemy” or “competitor” strains to slow it down or to mitigate the effect. The ones that grow fast are likely to be fairly harmful, and they are likely to grow in very high concentrations. The fact that commercial pasteurized dairy products are stored for long periods of time in production, transit, and then on the grocery store shelves means that there is ample time for them to grow to very high levels. Levels NOT seen in fresh raw milk.

Raw milk, on the other hand, is chock full of a full complement of bacteria and fungi. If you leave it out at room temperature without ever putting it in the fridge, it will develop into buttermilk. Buttermilk is just old fashioned “sour milk” which old recipes call for (they are not asking for that nasty stuff that pasteurized milk turns into when it gets too old).

Note: Buttermilk is just raw milk left out to sour. The cream rises and firms up, which makes it easier to skim. The milk left behind was “buttermilk”. The cream was then churned into cultured butter, and the milk from around the butter was poured off and added back into the buttermilk. Just so we understand why sour milk was called Buttermilk.

Refrigeration does affect it some. It will develop a different complement of microbes at higher temperatures than it does at low temperatures, but they are generally equally healthy.

So, when your raw milk turns a little off, what can you do with it? Turns out you have a lot of options!

NOTE: It is still healthy enough to drink. You can drink it as long as you do not mind the flavor. There is no need to worry that you have to “catch” it before it goes the least bit off to save your kids from being harmed, or to avoid ingesting something dangerous. It is just milk, with a little more probiotic benefit.

1. Make Biscuits. Southern buttermilk biscuits are a natural for sour raw milk, and so are buttermilk pancakes. You can omit the Baking Powder and use 1/3 that amount of baking soda which will react with the sour milk. You can also use it in any other recipe calling for milk, depending on how far off the flavor is, including things such as custards, milk gravies, and even home made macaroni and cheese or alfredo sauce. All of these cooked options will kill both the beneficial and harmful bacteria and fungi.
2. Make Smoothies. If you usually use yogurt or kefir in smoothies, sour raw milk is a good substitute. Bet nobody even notices! Microbes are kept intact.
3. Make Cheese. Let it sour a bit more, out at room temp for a day or so. Dump it in a pot, and heat until curds form and separate – to the point where you cannot touch the side of the pot at the level of the milk without it stinging. Strain, and either use as fresh cheese or press to make a hard cheese. You can also substitute it in any cheese recipe for buttermilk. Cooked cheeses result in a pasteurized product. You can also simply strain it without cooking if it has curdled, and use it as a soft cheese. It will be VERY full of microbes.
4. Pasteurize it and make yogurt or kefir from it. You CAN do either one without doing so – they are, after all, just variations on sour milk! This process kills anything that might be lurking in your milk, and replaces the microbial assortment with a cultured assortment (which isn’t that different in kefir than it is in ordinary sour raw milk, by the way!).

There does come a point where it is too far gone – but that is quite a bit further along than most people think! Milk that should NOT be used will be discolored (more than just a little yellowing), it will have mold on it, or a very unpleasant smell. You won’t generally mistake if it is too far gone.

Sour milk is actually one of the benefits of using raw milk. Our ancestors knew this, and had uses for fresh sweet milk, and uses for aged sour milk.

The more I use it, the braver I get. I started with just using it in baked goods and cheeses, but we now use it in many other ways. My favorite is probably smoothies – my probiotic smoothies have single-handedly healed a number of annoying health issues for me.

NOTE: Because of the rabid “sterilize everything” Nazis, and various government entities which subscribe to the theory that killing everything must be better than retaining any kind of natural balance, I am compelled to leave a disclaimer. This is my opinion. It is based on broad research and experience, but it is still my personal view, provided for informational or entertainment purposes (making buttermilk biscuits is great fun). Use it as you see fit AT YOUR OWN RISK. I am not recommending this to heal or treat any disease, and am not a medical professional, nor a health or nutritional professional.