How to evaluate dairy products after their “best by,” “use by” or “sell by” dates 

The world of dairy products is vast, and includes some foods that can last a while, others that quickly spoil in obvious ways, and still others, like soft cheeses, that can be riskier to eat after their “use by” dates, even if they look fine. Here’s what you need to know. 

Can you drink milk after its “sell by” date?

Yes! If the milk has been handled properly it should still be fine to drink after its “sell by” date (most standard milk bears a “sell by” date rather than a “use by” or “best by”). The “sell by” date is for the store’s inventory management and is not a safety date. While there are no national standards for milk shelf life labeling, the “sell by” date likely allows for some time in the consumer’s kitchen. That said, milk is obviously a pretty perishable food and you don’t have that long to use it. 

Rather than get hung up on the date, remember that fresh milk will usually tell you when it’s on its way out via some off odors and flavors (for a deep dive into spoiling milk, pinch your nose and check out this post). But even then, those early hints of spoilage don’t mean the milk will make you sick. Rather, it’s time to use it in a dish where the flavor won’t matter as much (like these pancakes). Spoilage bacteria, not human-disease-causing bacteria, are the usual culprits when milk spoils, so slightly-off milk is unlikely to sicken you. Still, in the remote chance a human pathogen is present, it will have had more time to grow and become more infectious in milk with more obvious spoilage. So, we advise using slightly-off milk in cooked dishes and avoiding serving it to those with weakened immune systems. 

To maximize your milk’s shelf life, make sure your refrigerator is set to 40 degrees or less, which will stall microbial growth. If your fridge (or your grocer’s or the delivery truck’s fridges) aren’t cold enough, milk could go bad before the “sell by” date.  Also, psychological factors can play a role. An Ohio State University study found when participants saw milk past its printed date they were more likely to throw it away than milk without a printed date. 

How to evaluate hard cheese past its “best by” date.

Many manufacturers use “best by” on hard cheeses and other low-moisture dairy products that are not closely associated with the growth of disease-causing microbes. As long as you’ve kept your hard cheese in the fridge, you absolutely have some leeway to use it after the date passes.

The less moisture a cheese contains, the less likely it is to support the growth of problematic bacteria. That’s why you’ll sometimes see dry cheeses like Parmesan stored at room temperature at the store. 

But, if you neglect cheese long enough its fats can go rancid. It’s also possible that mold, which grows slower than bacteria, but needs less moisture and can tolerate colder temperatures and more acidic conditions, could settle in. And even if a cheese is safe to store at room temperature, rancidity and mold growth are slowed at refrigerator temperatures and the cheese will last longer if it’s kept cold.

Both rancidity and mold growth are more likely once the package is opened and exposed to the environment. If you see a small amount of fuzz or other mold growth, you can cut it off; the USDA advises at least a one-inch margin. If the cheese is coated in tufty growths, it’s best to dump the whole thing.  (But, some harmless white crystals can also form on cheese. Check out this post for more on how to tell the difference between cheese crystals and actual mold.) 

I’ve seen some hard cheeses at my local grocery store bearing “use by” dates that are far in the future. As long as the cheese is aged and has very little moisture, I treat those “use by” dates as “best by” dates and assume the top concern is quality and that any issues would be obvious (like mold growth or off odors). Soft cheeses are a different story, as we explain below. 

How to assess brie, queso fresco and other soft cheeses past their use-by dates (and how they’re different from things like cream cheese)

Soft cheeses like brie and queso fresco can nurture listeria bacteria; these harmful bacteria can boost their numbers, and therefore their risk of causing illness, over time, and make certain “use by” dates worth paying attention to. Varieties of soft cheeses that aren’t acidic, have high moisture levels and often touch various surfaces when they’re prepared, cut and packaged are riskiest. Soft cheeses are extra risky if they’re made with raw milk, but even if they’re made with pasteurized milk they can still be contaminated with listeria after pasteurization. 

Cream cheese and other cheeses in “tubs” can last longer

But, while you might reasonably consider cream cheese or cottage cheese to be “soft cheeses,” they don’t carry the same listeria risk and you’ll likely have more leeway on their printed dates. In fact, the CDC suggests cream cheese and cottage cheese as alternatives to cheeses like brie for people in high-risk groups.

Nicole Martin, associate director of the Milk Quality Improvement Program at Cornell University, told me that cream cheese, for example, is often packaged while hot. That means heat should have killed any bacteria and there were no chances for the cheese to be contaminated before the tubs were sealed and cooled. Cream cheese and sour cream are also acidic, making for a more hostile environment for bacterial growth.

How to evaluate acidic dairy products, like yogurt, after the “best by” date

As long as they’ve been properly handled and look and smell fine, acidic dairy products like yogurt and sour cream can also be fine after their dates have passed (for more, check out this post about some “ancient” yogurt). The naturally occurring acid that gives yogurt its tart flavor checks the growth of problematic microbes. If the yogurt container remains unopened it’s as contamination-free as the day it was packaged at the factory (and if it was somehow contaminated at the factory, you might see mold like this or otherwise detect something amiss when you first open it). And once yogurt is opened, it can still last a while. But make sure to keep it in the fridge and scan any old yogurt with your eyes and your nose to make sure it’s still good. And keep in mind that, with enough time, the yogurt could break down chemically, which would also make its flavor and texture unappealing.