You bought a quart of buttermilk for a batch of pancakes, used a cup, and now the rest is sitting in your fridge. The recipe you bought is ready. The date of the cardboard is fast approaching, and you are not sure if you should use it, throw it away or it was doubtful to start. So does buttermilk go bad?
Does the butter go bad?
Short answer: Yes, buttermilk goes bad, but its natural acidity gives it a longer shelf life and is more forgiving than regular milk. An opened carton lasts 1-2 weeks in the refrigerator. Unopened buttermilk is usually good for 1 to 2 weeks from the printed date. Spoiled buttermilk develops blue-green molds, a strong aroma that differs from its normal aroma, or a thick, shiny texture that doesn’t thin out when shaken.
For more information on storing dairy products, see Food storage guide.
- Opened carton: 1 to 2 weeks refrigerated (USDA FoodKeeper: 1 to 2 weeks total)
- Unopened: 1 to 2 weeks from printed date if kept refrigerated continuously
- A sour smell is normal. Bad smell, not very sharp.
- Grainy texture is normal. It’s not a thick, shiny, cheese-like texture.
- Freezing works well and is the best use of an almost expired carton
- Butter powder: stable, lasts up to 2 years unopened
How long does buttermilk last?
Butter is a cultured dairy product, meaning lactic acid bacteria have been added to pasteurized skim milk to create the somewhat thick, lumpy product you buy at the store. This acidity is what gives buttermilk its distinctive taste, and it’s also what makes buttermilk last longer than regular buttermilk. A low pH (about 4.5) creates an environment that slows the growth of spoilage organisms.
According to USDA FoodKeeper, buttermilk keeps for 1-2 weeks in the refrigerator. America’s Test Kitchen, which researched this issue extensively with dairy industry experts, found that buttermilk won’t actually go bad (meaning, visible mold will develop) for up to three weeks after opening if it’s kept constantly 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 within two weeks of opening, trust your senses for the date, and freeze anything you won’t finish in time.
| The type | Refrigerator (Unopened) | Refrigerator (Open) | the freezer |
|---|---|---|---|
| Liquid milk (carton) | 1-2 weeks after printed date | 1 to 2 weeks | 3 months |
| Powdered milk (unopened) | 1 to 2 years at room temperature | 6 to 12 months in the refrigerator in an airtight container | It is not recommended |
How to tell if buttermilk has gone bad
Buttermilk is naturally sour, slightly thick and slightly grainy. These are not signs of deterioration. They are what fresh buttermilk should look and smell like. The challenge with buttermilk is that all of its normal characteristics overlap with early signs of spoilage in other dairy products. Here’s how to tell the difference.
- Blue-green or pink mold: The most definitive sign. Throw away the whole carton. Do not try to pull out the affected area.
- Intense fragrance: Fresh milk has a sour smell. Spoiled buttermilk smells sharp, rancid, or really unpleasant in a way that differs from its normal flavor. If you have to wonder if it smells bad, it probably doesn’t. If you worry, throw it away.
- Glossy or chunky texture that doesn’t thin out when shaken: Buttermilk naturally separates into a thicker body with some small lumps. A vigorous shake should reabsorb it into a pourable liquid. If shaking doesn’t work and the contents come out in large, cheese-like chunks, it’s spoiled.
- Yellow or colored liquid: Fresh buttermilk is white or very white. A yellow or gray body indicates spoilage.
Normal vs. corrupted: Key separation
Most people throw away perfectly good buttermilk because they mistake normal qualities for spoilage. Here’s a light side by side:
- A sour, sour smell
- Slightly thicker than milk
- Some liquid separation on the top of the box
- Small lumps or kernels that break up when shaken
- White color and very little white
Spoiled Butter:
- Odor intense, drawn or sharp, sour outside the normal
- A thick, glossy or chunky texture that doesn’t flow when shaken
- Blue-green, pink or dark mold is visible
- Yellow, gray or significantly discolored liquid
The easiest test: shake the cardboard vigorously. Fresh buttermilk, even when separated, will recombine into a pourable liquid. Spoiled butter will not be.
Can you freeze butter?
Yes, and unlike half and half or heavy cream, buttermilk freezes quite well for baking and cooking. America’s Test Kitchen recommends the ice cube tray method: Pour the butter into an ice cube tray, freeze until solid, then transfer the cubes to a freezer bag. Each standard cube holds approximately 2 tablespoons, making it easy to scoop out what you need for a recipe without defrosting the entire batch.
Frozen milk keeps for 3 months and is best used straight from frozen in cooked applications: pancakes, biscuits, waffles, quick breads, marinades and salad dressings. The texture changes slightly after freezing and thawing, making it less ideal for straight drinking, but works well for baking in most applications with minimal difference in quality. Thaw overnight in the refrigerator or add frozen cubes directly to a warm egg.
See also
Why buttermilk lasts longer than regular milk
Buttermilk’s long shelf life comes from its acidity. The lactic acid bacteria used for cultivation produce lactic acid as a by-product, which lowers the pH to around 4.5. Most spoilage bacteria and pathogens do not grow at this pH level. Regular milk has a pH of around 6.7 to 6.9, which is a more hospitable environment for bacteria. This is also why recipes that use buttermilk as a marinade (eg buttermilk fried chicken) are very effective: the acidity helps tenderize the meat, and the low pH slows the growth of bacteria on the surface.
This does not mean that buttermilk is immune to spoilage. After enough time or poor storage conditions, the natural acidity of buttermilk is also overcome by molds and other organisms that thrive in acidic environments.
What about buttermilk powder?
Powdered milk is a completely different product to liquid buttermilk, and it’s worth knowing if you occasionally smoke with buttermilk but can’t seem to finish the carton in time. The moisture has been removed from the dried milk powder, leaving the solids and the same acidic and salty flavor profile. Unopened, it will keep at room temperature for 1-2 years. After opening, transfer to an airtight container and refrigerate to extend its shelf life up to 6 to 12 months.
For baked goods, add the powder to the dry ingredients and replace the liquid with water. Most brands, including SACO, call for 4 tablespoons (1/4 cup) of powder to 1 cup of water to replicate 1 cup of buttermilk. The flavor is very close to fresh, although some bakers find it a little more tangy in the finished product.
Recipes that use buttermilk
If you can get a cardboard close to the end of the window, use it. Buttermilk works on that cinnamon pecan crunch banana breadand it’s great in pancakes, biscuits, fried chicken marinades and any quick bread that requires baking soda, as the acid reacts with the baking soda to leaven. Beyond baking, stir a splash into mashed potatoes instead of regular milk for a tangier result, add to soups instead of cream for a lighter body, or use as a base for a simple salad with olive oil and herbs.
Frequently Asked Questions: Is it OK to use buttermilk after the expiration date?Often yes, for baking and cooking. Buttermilk’s natural acidity means it’s more forgiving from its printed date than most dairy products. A carton that has been kept in the refrigerator continuously can be unopened 1 to 2 weeks after the date. The opened carton depends on when you opened it: use within 2 weeks after opening, regardless of the date. Always check the smell and texture before use. For cold drinks or salad dressings, keep closer to the date for best flavor.
Frequently asked questions: Why does milk smell sour? Is that bad?no Buttermilk is said to smell sour. It is fermented milk made by culturing milk with lactic acid bacteria, which produce lactic acid as a byproduct. This lactic acid is responsible for the pungent and long-lasting smell. A mild or sour smell is quite normal. The smell that indicates the mixture is sharper, more scratchy, or really unpleasant, in a way that clearly differs from the touch of buttermilk. If you are not sure, shake the cardboard and check the texture. If it flows normally and smells slightly sour, it’s almost certainly fine.
Further reading
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