Traditionally, buttermilk is the leftover liquid that remains after straining milk fat during butter production. Despite its name, buttermilk is low in fat and a good source of protein, providing up to 8 grams in a single cup (250 mL) (1).

Buttermilk has a tangy flavor and is naturally thicker compared with regular milk. Its higher lactic acid content lends itself well to baking, and the product is widely used in bread production, pancakes, and other quick breads (2, 3).

It’s also widely consumed as a drink, made into cheese, or added to sauces and dips for a boost in flavor and smoother consistency (2, 3). 

However, because of its tangy taste, many people have trouble telling when their buttermilk has gone bad and is no longer safe to use.

This article tells you all you need to know about buttermilk and how long it lasts.

Cultured vs. traditional buttermilk

The buttermilk you buy at your local grocery store — also known as cultured buttermilk — is usually different from traditional buttermilk originally produced on a farm.

Cultured buttermilk follows a similar manufacturing process to yogurt. Bacterial cultures (Lactococcus lactis ssp. lactis), salt, and citric acid are added to skim milk and ferment for 14–16 hours. This converts milk sugars into lactic acid, producing a tangy flavor (4, 5).

In contrast, traditional buttermilk is a byproduct of the butter-making process. It’s the liquid that remains from separating the fat from cultured butter.

Compared with cultured buttermilk, traditional buttermilk is less tangy and sour (4).

Buttermilk must be pasteurized for sale in the United States, meaning it undergoes a heat treatment of 161°F (71.7°C) for at least 15 seconds, allowing for a longer shelf life and killing off harmful bacteria (6). 

Though most buttermilk available in stores is cultured buttermilk, many chefs and culinary experts rely on traditional buttermilk for its better flavor and texture.

summary

Cultured buttermilk is made from skim milk with added bacterial cultures, salt, and citric acid. In contrast, traditional buttermilk is the remaining liquid from cultured butter during the butter-making process.

Shelf life

Keeping an eye on the shelf life of buttermilk can ensure you’re getting the best and safest product.

Buttermilk contains lactic acid and a compound known as diacetyl, which both contribute to its tangy and buttery flavor. Over time, buttermilk continues to sour and the bacteria that produce diacetyl decline, resulting in a less flavorful product (4).

If you’re concerned that you won’t use your buttermilk before it expires, freezing it may be best. However, freezing buttermilk will alter the texture and flavor of your product and usually only works well in baking.

Avoid purchasing unpasteurized buttermilk which can increase your risk of foodborne illness (7).

Using buttermilk within its recommended time frame ensures your product tastes great and is safe to consume. Use the following chart as a reference:

Buttermilk (unopened)Buttermilk (opened)
Refrigeratorup to 7–14 days past expiration dateup to 14 days after opening
Freezer3 months3 months

If you choose to freeze your buttermilk, you can freeze it in its original container as long as it has enough space. This helps the package to expand in the freezer and prevent it from bursting. Otherwise, ensure you put the buttermilk in a sealed, airtight container.

However, buttermilk may go bad before the expiration date due to improper handling, fluctuating temperatures, or other factors. Therefore, look for other signs that your buttermilk has gone bad, which are discussed below.

summary

Buttermilk can last up to 14 days in the fridge after it has been opened and may last beyond its expiration date if unopened. However, it’s always best to use it as soon as possible.

How to tell if buttermilk has gone bad

In addition to its expiration date, other signs that your buttermilk has gone bad may include:

  • thickening or chunks
  • visible mold
  • strong odor
  • discoloration

Generally, if it looks different from when you purchased it, that’s a red flag.

Though these are general signs to look out for, if you’re concerned that your buttermilk has gone bad, it’s best to discard it to prevent getting sick.

summary

If your buttermilk has any changes, such as smell, texture, color, or mold growth, it’s time to throw it out.

How to extend buttermilk’s shelf life

If you’re trying to keep your buttermilk for as long as possible, be sure to practice proper hygiene when handling it. For example, keep your hands clean, avoid coming into direct contact with the lip of the bottle, and don’t drink directly from it.

Like most dairy products, buttermilk should always be refrigerated below 40°F (4.4°C) to prevent widespread growth of bacteria. Avoid storing it in the door of your fridge, which usually experiences the most temperature fluctuations.

Avoid leaving buttermilk out at room temperature. Put it back in the fridge immediately after use to prevent it from reaching the danger zone — a temperature range of 40–140°F (4.4–60°C) at which bacteria growth rapidly increases (8).

Finally, if you’re concerned about food waste, purchase the smallest size available and use it within its recommended shelf life.

summary

To keep buttermilk from going bad too soon, practice good hygiene and store it in the coldest part of the fridge below 40°F (4.4°C).

The bottom line

Buttermilk is a delicious, tangy beverage that tastes great by itself and lends itself well in many baking and cooking applications.

Most buttermilk available in stores is known as cultured buttermilk, which is made differently than traditional buttermilk. However, both have short shelf lives and should be stored in the fridge below 40°F (4.4°C).

Opened buttermilk can last up to 14 days in the fridge and slightly longer than its expiration date if unopened. It can be frozen opened or unopened in an airtight container for up to 3 months.

If you notice any changes to the smell or look of your buttermilk, it’s best to toss it to avoid getting sick.