There's no need to buy buttermilk when it's so easy to make at home from heavy cream. No other ingredients are required, and you don't even need a churn. It's a quick and simple process that will result in the freshest buttermilk you've tasted. Try it once and you'll be hooked while saving a little money on something that often goes to waste.
Even though the heavy cream is the only ingredient you need, it's best to shop smart. Your buttermilk will turn out best if you avoid a cream that is ultra-pasteurized. The regular pasteurized cream has a fresher taste because it isn't subjected to the very high temperatures used in the "ultra-pasteurization" process. It can be more difficult to find but is worth it.
To make a small batch of homemade buttermilk, fill a jar halfway with heavy cream. Then, screw the lid on firmly (a canning jar works well for this purpose). Start shaking the jar up and down. After several minutes, the cream will thicken and turn into whipped cream.
Keep shaking until the whipped cream is replaced with a yellow glob (that's butter) and a separate liquid (that's the buttermilk). Pour the buttermilk out of the jar and use it in any recipe that calls for it—or drink it straight, as they did in the olden days.
That's a lot of shaking, though it does the trick when you need just a little buttermilk. If you need a larger batch, pour the heavy cream into a mixer and beat it at high speed. It will also turn into whipping cream first but if you keep whipping, it will separate out into butter and buttermilk.
Don't Waste the Butter
The really neat part about this trick is that you're actually making two ingredients at the same time. There's no need to let that butter go to waste, you just need to process it a bit to make it useable.
Knead the separated butter under cold water for a couple minutes to remove any remaining buttermilk. It will spoil very quickly if you skip this step. Then salt your butter if you like and store it in the refrigerator until you're ready to use it. Homemade butter has a relatively short shelf life, so enjoy it within a few days.
Two Kinds of Buttermilk
Store-bought buttermilk isn't real buttermilk at all. Instead of being made from heavy cream, it's made from low-fat milk that is soured by adding lactic acid bacteria, much like yogurt. Technically, this type of buttermilk is referred to as cultured buttermilk.
The processes used makes for some pretty big differences between the two. Cultured buttermilk tastes sour and has a thick consistency. Real buttermilk is sweet and is much thinner.
Perhaps the biggest difference is that cultured buttermilk is acidic. If you're working on a baked good that calls for buttermilk, like a traditional Irish soda bread recipe, you need to stick to store-bought.
In these recipes, cultured buttermilk is, more than likely, used to activate the baking soda. That's something that real buttermilk cannot do. The good news is that you can also make a cultured buttermilk substitute. All you need for that recipe is milk and lemon juice or vinegar.
If you need buttermilk regularly but don't normally stock heavy cream, there is another option. Simply keep powdered buttermilk on hand and you can mix up a batch whenever you need it.