Make Sour Milk From Raw Milk

  Steaming Boil

Sour milk is a fermented, probiotic-rich cultured dairy food you can easily make with raw milk. A terrific technique to use up older and surplus raw milk, sour milk has many uses in recipes and beyond.

carafe of sour milk
Left in a warm spot in your house, the good bacteria in raw milk will naturally flourish and sour.

Traditionally made sour milk done in the old way from raw (unpasteurized) whole milk that has been left out somewhere warm to naturally turn is a healthful dairy product that has an incredible array of uses. It is also a powerful natural probiotic.

Using soured milk is an old way to leaven bread without the use of yeast, but you can also drink it straight for its pleasantly sour taste. Or ferment it even further until it thickens and separates into curds and whey and eat it as you would yogurt. If you have older raw milk kicking around — do not let it go to waste. Make sour milk instead.

You absolutely must use raw (unpasteurized) milk to make real and safe sour or “clabbered” milk. Pasteurized milk will not contain the good bacteria that flourish at room temperature.

Spoiled Milk

What is the difference between soured milk and spoiled milk?

Soured milk is raw milk, usually whole milk, that has been left out at room or warmer temperatures for a period of time until it becomes slightly thicker and takes on a sour taste.

The timeframe is usually around 24 hours for this process to occur.

Spoiled milk is milk that has gone bad and is not fit for consumption. It can also be quite dangerous as it’s teeming with all sorts of bacteria, many of which are hostile to the human digestive tract. Milk that has spoiled will not have the pleasantly sour, fermented taste of soured or clabbered milk but will taste and smell absolutely disgusting. Your nose will tell you that the milk is bad.

Please note that dangerous pathogens can flourish and multiply in any milk whether it smells or tastes “off” or not. This is true for unpasteurized and pasteurized milk alike.


Then there is also buttermilk which is the liquid leftover from the butter-making process. It can be made from sweet cream or cream that has been left to culture (i.e ferment) at room temperature for about 24 hours.

I describe this process in great detail here: Raw Cream Cultured Butter or Sweet Cream Butter Recipe | Traditional European Butter Techniques

Sweet & Acid Whey

And of course, there is also whey which is the liquid leftover from the cheesemaking process. There are even two types of whey, the first is acid whey which results from making vegetarian cheese like paneer, which is the easiest cheese to make and also freezes beautifully.

The second is sweet whey which is leftover from renneted cheeses. Rennet is the enzyme found in a calf’s stomach.

Whey is a protein-rich drink with many uses besides.

Clabbered Milk or “Bonny Clabber”

Clabbered milk or bonny clabber (Bainne Clábair) is a type of soured milk. Bonny clabber is, again, raw whole milk left out at room or warmer temperatures until it sours and thickens up even more than simple soured milk. Clabbered Milk is the same as Curds & Whey as it will separate into thick sour curds leaving the whey at the bottom.

Clabbered milk can be considered a type of yogurt.

In my experience, this process to make clabbered milk can take as long as 72 hours but it depends on your kitchen and climate.

Soured milk does not ferment long enough for this separation to occur and that is its key difference from clabbered milk.

Sour Milk Substitute

You may have come across recipes that advise you to just add some vinegar or lemon juice to milk as a shortcut to making soured milk, a substitute for the real thing..

And although this will work in a pinch but it is not even remotely close to true sour milk.

However, if you need some RIGHT NOW for a baking project — add 1 tablespoon of plain vinegar or lemon juice per 1 cup of milk and after letting that sit for 5-10 minutes you will have a facsimile that would work decently enough in something like Traditional Irish Soda Bread.

You can use pasteurized or raw milk for this technique, but again, this is not true sour milk and I recommend trying out the real stuff if you can.

raw kefir smoothie in mason jar
Try using sour milk in a smoothie, like in my nutrient-dense raw kefir smoothie recipe. Just swap out kefir for sour milk.

Recipes With Sour Milk

  • My historic recipe for Irish Soda Bread Using Einkorn Wheat depends on sour milk (or buttermilk) to leaven the bread.
  • You can also use sour milk instead of kefir in my Raw Kefir Smoothie With Berries, Collagen, & Egg Yolks Recipe

10 More Practical Uses

There are many uses for soured milk. Here are just a few.

  • Drink it on its own. Why buy expensive probiotic supplements if you have access to nourishing raw milk? It’s teeming with beneficial gut bacteria.
  • Use it to ferment and make chicken feed more nutritious and last longer.
  • Or just feed it directly to your livestock.
  • Remove the bitterness from liver. Soak your liver in soured milk for 4-8 hours, or even overnight. This will remove any bitterness and may win over liver haters.
  • Tenderize meat. Soured milk will tenderize any tough cut of meat you have.
  • Bake/cook anything. Any recipe calling for buttermilk can generally also be substituted with soured milk. There are a ton of recipes out there for fried buttermilk chicken, cookies, pancakes, scones, cake etc.
  • Soak grains. Properly prepare your grains by soaking them in soured milk. This process will render many of the toxic anti-nutrients naturally found in grains inert or at least greatly diminish the effect. I use this technique in the Soda Bread Recipe.
  • Gardening. Dilute the soured milk with plain water and use it as a nourishing source of calcium and other things in your vegetable gardens.
  • Skincare. Lactic acid is a common and powerful ingredient used in skincare. It exfoliates the top layers of your skin leaving it refreshed and glowing. Try this once a week to start. Just rub some soured milk on your face and wash it off after about 20 minutes before applying your moisturizer. Can be used after a deeper pore cleansing salicylic acid treatment too.
  • Leave it out longer until it separates into curds and whey — make clabbered milk or bonny clabber. This can take up to 72 hours but will depend entirely on the conditions (temperature and humidity) of your kitchen. Enjoy plain or spiced with cinnamon, nutmeg, maple syrup, raw honey etc.
a carafe of sour milk next to some cheeses