How To Tell Your Butter Has Gone Bad and Should Be Tossed

With a slew of unspoilable basics in your pantry like sugar, salt, and vinegar, it’s easy to assume that butter falls into the same category. Its best-by date always seems so far in the future, and even the United States Department of Agriculture (USDA) says it’s OK to leave it out at room temperature for two days, a fact that clearly separates it from other forms of dairy.

Does butter go bad? And if it does, how can you tell? If you’ve discovered a months-old, half-wrapped piece in your fridge and spread it on your morning toast, you probably already know the answer. Here’s what I found out.

Does Butter Go Bad?

Unfortunately, butter does eventually go bad. I spoke to a representative at Kate’s Butter (my favorite brand of butter) who told me that butter’s best-by date is one you should really pay attention to.

Your butter will indeed begin to decrease in quality after the best-by date. The rep noted that it “usually indicates the fats are beginning to turn rancid.”

Rancid butter has an unmistakable off flavor that you may have encountered tasting old oil, old nuts or seeds, or any other food with a high-fat content that is long past its prime.

Kate’s rep explained that it’s best to go by the best-by date because (depending on the brand) there’s no guarantee that the butter was recently made. Larger producers will often buy cream in bulk in the spring when it’s most available, hold it in cold storage for a long period of time, and eventually soften and repackage it for times of the year when butter is in higher demand, like the holidays.

How You Tell Your Butter Has Gone Bad

With the help of your senses, it should be fairly clear when your butter has gone rancid. Spoiled butter will have a sour, bitter taste, and may also change in color and give off a subtle, unpleasant odor. 

It may also taste like the other foods in your refrigerator, as it quickly absorbs the flavors of any strong-smelling ingredients in its vicinity. The rep from Kate’s told me, “If you put it near an onion, it’s gonna taste like an onion.”

2 Tricks for Keeping Butter Fresher for Longer

1. Refrigerate the Butter

The best way to keep your butter fresh and extend its quality is to keep it in the refrigerator, softening it to room temperature only when needed.

2. Buy Butter Wrapped in Foil

The Kate’s rep also suggested looking for butter brands like Kate’s, who package their butter sticks in foil instead of parchment. Parchment allows odors to absorb into butter with very little protection, while aluminum foil provides a strong barrier from outside environments, be it your grocery store’s dairy case or your own refrigerator.

Because aluminum is more expensive than parchment, most brands tend to go with the less expensive material, but it’s a little change that makes a big difference.