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Don’t Trust Your Carton’s Sell-By Date — Here’s How to Really Tell When Milk’s Gone Bad


If you’re wondering how to tell if milk is bad, you’re not alone. Many consumers out there are confused about the sell-by dates on milk cartons. Little do they know that a whole lot of perfectly good milk is constantly going to waste, according to food experts.

Research published in the August 2018 issue of Journal of Dairy Science detailed a new predictive model that examines spore-forming bacteria and when they emerge in our favorite breakfast beverage. The Cornell University food scientists behind the research hope that this can make sell-by and best-by dates on milk cartons more precise in the future, because many of them are inaccurate or misleading at the moment.

“Putting dates on milk cartons is a big issue, because consumers often discard the milk if it is past the sell-by date,” said senior author Martin Wiedmann in a press release. “Often there is little science behind those dates, as they are experience-based guesses. The goal of this research was to put good science to use, reduce food waste, and reduce food spoilage.”

For instance, the researchers found that the harmful spores can be reduced in microfiltered milk products — which are steadily growing in popularity — simply by lowering the refrigeration temperature. When they reduced the fridge temperature from 42.8 degrees to 39.2 degrees, only 9 percent of the milk half-gallons were spoiled after 21 days, compared with 66 percent of the half-gallons held at the higher temperature. That said, it’s worth keeping in mind that microfiltered milk products are not available in every grocery store.

Wiedmann says he hopes to see more accurate use-by dates on all milk cartons in about five or eight years — perhaps with scannable barcodes that give consumers the most accurate and up-to-date info about what they’re buying and how long milk is safe to drink. But in the meantime, there are a few handy ways to tell if milk is bad that have nothing to do with the date stamped on the carton or bottle.

How to Tell If Milk Is Bad

As you’re probably aware, you really don’t want to drink spoiled milk. Not only does it pack a stomach-churning taste, it can also be full of harmful pathogens that could potentially cause a nasty bout of food poisoning. Luckily, it’s easy to avoid drinking bad milk, thanks to a helpful three-part test.

  1. Take a whiff before you take a sip. One of the biggest signs of spoiled milk is a sour odor, according to the Clemson College of Agriculture, Forestry, and Life Sciences. If the odor alone makes you wince and crinkle your nose, don’t even think about putting it in your breakfast cereal.
  2. Closely examine the milk’s appearance. Spoiled milk’s texture is usually not the same as fresh milk. Instead of a smooth liquid texture, spoiled milk often includes a curdled consistency: It’s not pretty to look at, and it’s definitely not pretty to swallow, either.
  3. Do a taste test. If the milk looks and smells all right to you, try tasting a little bit of it (this is not the time to glug if you’re still unsure). As long as the flavor is not “off” in any way, you can likely feel safe to drink it with confidence.

Next, learn about the tastiest superfoods that can help you live longer in the video below:

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