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What is Buttermilk?

Buttermilk is the baker’s secret to tender baked goods. In this post, I’ll share what it is, why it is used in many recipes, and what to do if you don’t have any on hand.

Pouring buttermilk into a glass jar

What is buttermilk?

Traditionally, buttermilk is the liquid left over after fermented cream is churned into butter. It was said to be a very delicious and refreshing drink with many health benefits. 

However, today commercially available buttermilk is low fat or nonfat milk that has been inoculated with a bacterial culture to simulate the naturally occurring bacteria in the traditional product. The bacteria convert lactose found in milk into lactic acid and increases the acidity of the milk, which lends buttermilk both its thickness and tartness.

Some dairies add yellow flecks to cultured buttermilk to simulate butter flecks left over from the churning process.

What does buttermilk taste like?

Cultured buttermilk is thick and tart. It is not exactly my cup of milk, but I love using it in baking.

Buttermilk inhibits gluten formation

Baking is all about chemistry, and acidity plays an important role. First, we need to revisit Gluten! Gluten gives baked goods their structure. This goes for bread, cookies, cakes, etc.  And acid can alter the quality of gluten. 

Acidity in the dough increases the number of amino acids along the protein chains, which make up gluten. These amino acids increase the repulsive forces between these protein chains, pushing them apart, and weakening the gluten network (Harold McGee’s On Food and Cooking: The Science and Lore of the Kitchen). 

Now that might be a lot of words, but the two important points you’ll need are:

  • More gluten gives you chewy texture like in yeasted bread
  • And less gluten gives you, well, less chewy and more tender texture like in birthday cakes.

Buttermilk is acidic, and it plays a part in inhibiting gluten formation, which gives you tender and moist crumbs in cupcakes and muffins.

Leavening power

Buttermilk also plays a role in leavening baked goods. Since it is acidic, baking soda is the leavening agent of choice in buttermilk batter. Baking soda and lactic acid react to produce carbon dioxide which helps your baked goods rise. 

Pouring buttermilk into a flour mixture in a mixing bowl

Buttermilk Substitutes

In a pinch, if you run out of buttermilk or just don’t have any on hand, you can make homemade buttermilk using one of the following combinations to substitute for 1 cup of buttermilk:

  • 1 tablespoon (½ oz) of lemon juice + 7.5 oz of milk to make 1 cup
  • 1 tablespoon (½ oz) of vinegar + 7.5 oz of milk to make 1 cup
  • ½ cup of sour cream + ½ cup of milk
  • ½ cup of yogurt + ½ cup of milk

My favorite combo is lemon juice + milk. After whisking together, the mixture will thicken in about 5 – 10 minutes. The consistency actually looks like buttermilk.

Any of these combinations will not taste exactly like buttermilk and will alter the taste of your baked goods. But I really don’t think it is such a big deal, unless you have a super sensitive palate and cannot stand the taste of lemon (for example). In that case, you can pick a different substitute.

How to store leftover buttermilk

Most recipes don’t call for more than 1 cup of buttermilk. And I know it can be a pain to have so much leftover buttermilk when you only want to make a batch of muffins

It’s tempting to just skip over that ingredient on your list and use what you have in the fridge, which you can, by making homemade buttermilk (see above)! But due to its acidity, buttermilk has good staying power and will last 3 – 4 weeks in the fridge

I’ve used buttermilk past its printed expiration date without any problems. However, please use common sense as with any food. Since it is more difficult to check whether buttermilk has spoiled by smell, check the texture, if it is grainy or clumpy, it is probably bad. When in doubt, toss it.

Can I freeze buttermilk?

Absolutely, if you know you’re not going to use up all the leftover buttermilk within 3 – 4 weeks, portion and freeze it. Frozen buttermilk will separate when thawed, just whisk it well before using.

Like I said earlier, most recipes don’t usually call for more than 1 cup of buttermilk, so you don’t want to freeze the entire container of buttermilk just as it is. Divide it into 1 cup portions at most, or 1 oz (2 tablespoons) portions.

I like to use clean old jam jars or plastic deli containers (I usually save the ones that we get from the yogurt stand at the farmer’s market, they’re airtight and durable). These containers will be perfect to save 1 cup portions.

To save smaller 1 oz portions, measure and freeze buttermilk in an ice cube trays. When completely frozen, pop them out and store in a freezer bag or larger container.

Buttermilk in a glass jar standing next to a buttermilk carton

Test out the power of buttermilk in these recipes

If you make any of my recipes, please let me know! Leave a comment, send me a photo, rate it and don’t forget to tag me @wildwildwhisk on Instagram. I’d love to see what’s cooking up in your kitchen. Cheers!

This post was originally published on 8/15/2014. It was updated on 3/2/2020.

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