You bought a quart of buttermilk for a batch of pancakes, used one cup, and now the rest is sitting in your fridge. The recipe you bought it for is done. The date on the carton is coming up fast, and you are not sure if you should use it, toss it, or whether it was already questionable to begin with. So does buttermilk go bad?
Does buttermilk go bad?
The short answer: Yes, buttermilk goes bad, but its natural acidity gives it a longer and more forgiving shelf life than regular milk. An opened carton lasts 1 to 2 weeks in the refrigerator. Unopened buttermilk typically stays good for 1 to 2 weeks past the printed date. Spoiled buttermilk develops blue-green mold, an intensely foul smell distinct from its normal tang, or a thick, gloppy texture that does not thin when shaken.
For more on storing dairy products, see the Food Storage Guide.
Key Takeaways
Opened carton: 1 to 2 weeks refrigerated (USDA FoodKeeper: 1 to 2 weeks total)
Unopened: 1 to 2 weeks past the printed date if stored continuously cold
Sour smell is normal. A foul, intensely sharp smell is not.
Lumpy texture is normal. Thick, gloppy, cottage-cheese-like texture is not.
Freezing works well and is the best use for a nearly-expired carton
Buttermilk powder: shelf-stable, lasts up to 2 years unopened
How Long Does Buttermilk Last?
Buttermilk is a cultured dairy product, meaning lactic acid bacteria were added to pasteurized skim milk to create the tangy, slightly thick product you buy at the store. That acidity is what gives buttermilk its characteristic flavor, and it is also what makes buttermilk last longer than regular milk. The low pH (around 4.5) creates an environment that slows the growth of spoilage organisms.
According to the USDA FoodKeeper, buttermilk keeps for 1 to 2 weeks refrigerated. America’s Test Kitchen, which researched this topic extensively with dairy industry experts, found that buttermilk won’t turn truly bad (meaning develop visible mold) until at least three weeks after opening when kept continuously cold. University extension programs generally recommend consuming buttermilk within three weeks of the date stamped on the package.
The practical answer for most people: use it within two weeks of opening, trust your senses over the date, and freeze anything you won’t finish in time.
Type
Refrigerator (Unopened)
Refrigerator (Opened)
Freezer
Liquid buttermilk (carton)
1 to 2 weeks past printed date
1 to 2 weeks
3 months
Buttermilk powder (unopened)
1 to 2 years at room temperature
6 to 12 months refrigerated in airtight container
Not recommended
How to Tell If Buttermilk Has Gone Bad
Buttermilk is naturally sour, slightly thick, and a little lumpy. These are not signs of spoilage. They are how fresh buttermilk is supposed to look and smell. The challenge with buttermilk is that all of its normal characteristics overlap with early spoilage signs in other dairy products. Here is how to tell the difference.
Signs of Spoilage
Blue-green or pink mo
