Does Buttermilk Go Bad?

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Buttermilk was originally made from the liquid leftover after straining the fat while making butter. It’s thicker than normal milk and tastes tangier. Because it has a similar flavor and consistency to fermented milk, you may ask yourself, “Does buttermilk go bad?”

If you store it in optimal conditions in the fridge, an opened container of buttermilk should stay fresh for around two weeks. After that, it will get thicker, more acidic, and less suitable for drinking, but you’ll still be able to use it in pancakes and other cooked recipes.

Buttermilk can go off subtly and gradually. If you don’t already know the difference, it can be difficult at first to distinguish between its regular tang and its sour bite.

Here are a few tips that will help you keep your buttermilk fresh and help you tell when it’s not.

How Long Does Buttermilk Last?

If you think buttermilk looks and tastes like slightly-off milk, you’re not wrong. Technically, it is a kind of fermented milk, although it can still go off in its own way.

Buttermilk starts with two competing flavor agents, live lactic acid bacteria and diacetyl, which is a bacterial byproduct. Together, they give buttermilk its distinct buttery, tart taste.

As time passes, the diacetyl declines along with the buttery flavor, while the sour-tasting lactic acid continues to thrive. You can only store it for a limited time before it stops tasting like itself.

The shelf life of buttermilk should be around:

  • 2 weeks in the fridge in an opened container
  • 2 weeks past its expiration date in the fridge in an unopened container
  • 3 months in the freezer

According to USDA guidelines, opened buttermilk will stay stable in the fridge for more or less two weeks and in the freezer for three months.

If you leave it sealed in its original container in the fridge, it should stay drinkable for up to two weeks past its ‘Best By’ date.

These time frames change a bit depending on whether you’re going to drink your buttermilk whole, use it in an uncooked dish, or cook with it.

Fresh buttermilk is best for drinking and adding to uncooked recipes like homemade buttermilk ranch salad dressing. Raw buttermilk works best when the butter flavor is still strong.

After a couple of weeks, besides losing a lot of its buttery flavor, your buttermilk will probably look noticeably thicker than when you bought it.

Don’t worry, though, cooking with buttermilk is when the acid highlights of the buttermilk show really begin to shine. Aged buttermilk still works great for tenderizing meat and baking.

If you need to freeze your buttermilk, make sure there’s enough space in its original container for the inevitable expansion. If not, keep it from bursting open by freezing it in a larger airtight container.

Freezing buttermilk adds another volatile element to an already unstable situation with interesting effects. Below zero temperatures solidify the liquid water molecules first, which increases the acidity and encourages the molecules of casein to stick together.

This is the same curdling process that we believe happened to Little Miss Muffet’s curds and whey before the spider incident. Buttermilk separated is a nightmare to drink, but it’s still delicious in baked recipes.

Related | Does Butter Go Bad?

Is Buttermilk Supposed To Be Lumpy?

Even fresh buttermilk sometimes contains a few lumps. You can usually get rid of these by shaking the container vigorously.

As long as you can still pour it, you shouldn’t have to worry unless you notice the following problems.

How To Tell if Buttermilk Is Bad

If you haven’t been trained in the finer arts of buttermilk, it can be a little tricky to tell when it’s gone bad. Some indicative clues include:

  • Sour smell
  • Discoloration
  • Mold
  • Fizz
  • Clumpy texture

Your nose can tell the difference between buttermilk and regular milk, and you can also trust it to ferret out the smell of sour buttermilk. There’s a grey area when buttermilk has started to sour but is still usable.

If your nose is sending you mixed messages, you’re probably in the buttermilk twilight zone, so you’d better use it quick.

Next, check for a change of color. Souring buttermilk usually turns yellower than it was. It’s a subtle change, so you may have to really Sherlock this one out.

If your eyes and nose deduce from these elementary changes that something off is afoot, it may be safer to send your buttermilk to Baker Street and use it for cooking only.

Some more obvious signs of spoilage include mold and fizz. Buttermilk mold tends to be a bluish-greenish color and usually grows right on the surface. A few bubbles in your buttermilk can be fun, but if there’s a noticeable fizzing sound when you open it, it’s probably not safe to drink.

Lightly-lumped buttermilk is normal, but if it has more lumps than liquid, don’t use it.

Rich buttermilk should pass the Pour Test: If you can’t pour it, throw it out.

The best way to discard bad buttermilk is to drain it down the toilet. This will keep your kitchen from smelling temporarily unpalatable. Chase it with a cup of vinegar or a pinch of baking soda to help it go down the drain smoother.

Related | Does Vinegar Go Bad?

Can Old Buttermilk Make You Sick?

Most buttermilk you can purchase has been properly pasteurized to purge potential pathogens. That means even if you drink sour buttermilk, it probably won’t make you deathly ill.

Sour buttermilk can still cause mild food poisoning. It won’t kill you, but it can make you throw up and give you diarrhea, nausea, and plenty of stomach pain.

Don’t cry over spoiled buttermilk. Your stomach is strong enough to sort out a few accidental sips, but we don’t recommend drinking it in large quantities.

How To Store Buttermilk

Always keep buttermilk in the fridge. The shelf life of buttermilk falls precipitously if your shelf is at room temperature. Here are some other tips for storing buttermilk:

  • Avoid the fridge door
  • Use an opaque, airtight container
  • Keep the container’s mouth clean

Temperatures above 40 degrees Fahrenheit are a danger zone for buttermilk, but temperature fluctuations can also incite bacterial rebellions. The door of your fridge is its most volatile neighborhood. It quickly loses its cool every time you open it.

We recommend storing buttermilk in the back of the fridge, where cooler heads prevail.

There’s a reason buttermilk usually comes in an opaque container. Darkness is its friend. Try to keep its container closed as much as possible to keep the light and air out.

Don’t put your mouth on the container’s mouth. Drinking directly from the spout is a great way to introduce your buttermilk to mold, yeast and bacteria. Wash your hands before touching the opening, and pour it into a cup before drinking.

If you store it in the freezer, expect your buttermilk to separate. Buttermilk separated can be blended back together, but it will still taste acidic, so we recommend only using it for cooking.

Try to use frozen buttermilk within about two months, or you may not be able to use it at all.

Final Thoughts

Like vampires vs. werewolves, buttermilk is an age-old flavor fight between tangy bacteria and their buttery by-product. After a while, the tang will start to win, and the butter flavors will die out.

You can keep buttermilk alive as long as possible by storing it under 40 degrees Fahrenheit. In a sealed, nontransparent container, it will stay fresh for around 14 days in your fridge and around 90 days in your freezer. Avoid stomach problems by tossing it if it changes color or smell.