Reviewed by Dietitian Katey Davidson, M.Sc.FN, RD, CPT
Key Points
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Pasteurized milk can usually last a few days past the “best by” date if stored properly.
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Sour smell, curdling or color change are signs milk is spoiled.
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Milk left at room temperature over two hours should be discarded.
Most of us have been there—you’re rushing to make coffee before work, but as you pour your milk, you catch a whiff and suddenly wonder if it’s still safe to drink.
Milk has a shorter shelf life than many other foods, so this is a common concern. Most store-bought milk is pasteurized, a process that heats it to kill pathogens. But pasteurization doesn’t eliminate everything, explains food safety expert Brian Labus, Ph.D., M.P.H., REHS .
“Some spoilage bacteria are still present, and additional bacteria can be introduced once you open the milk,” says Labus. “Bacteria need sugar and water to thrive, and milk provides both of these.” That means that bacteria can grow much faster in milk than in drier products like cheese, causing it to spoil.
Sometimes it’s still hard to tell if milk has gone bad. We spoke with food safety experts about the signs that mean it’s time to toss your milk.
How Long Does Milk Last in the Fridge?
There’s no exact timeline for how long refrigerated milk will stay good. It depends on when the milk was packaged, not when you buy it, Labus explains. “The dates on the carton will give you an idea of how long you have to consume the milk,” Labus says. “But that doesn’t mean it’s unsafe to drink after that date.”
On milk containers, you’ll usually see a “best before” or “use by” date, or another similar term. These dates indicate the manufacturer’s estimate of when the product will have the best quality or flavor.
“There is no need to throw it away once it has reached that date if it still smells and tastes OK,” says food safety expert Ellen Shumaker, Ph.D . Though, this only applies if the milk has been stored properly.
Research shows that pasteurized milk kept at or below 40°F (4°C) can remain safe for around five to six days after the “use by” date. However, milk stored at higher temperatures may spoil sooner, even before the expiration date.
How to Tell If Milk Has Gone Bad
It Tastes Strange
If your milk tastes sour, acidic or off, it’s time to throw it out. “Microorganisms like bacteria and yeast produce enzymes when they grow, and these enzymes can break down the fats, sugars and proteins naturally present in milk,” explains Labus. “When this happens, the taste, smell or texture of the milk changes.”
The Texture Doesn’t Look Right
Fresh milk normally has a smooth consistency. If it starts to thicken, curdle or separate into fat and water, it’s likely spoiled.
The Smell Is Off
Milk may develop a pungent or sour smell as it spoils. The same microorganisms that alter taste or texture can also produce off odors. This happens “because bacteria release various compounds such as acid, as well as fats and proteins in the milk breaking down,” explains Shumaker.
The Color Is Different
Normally, milk is bright white. As it spoils, the color can become slightly yellow or more of a dull white. “But you will notice the smell long before the color change,” Labus says.
You Forgot to Refrigerate It
Refrigeration helps slow the growth of bacteria. Milk should not sit out at room temperature for longer than two hours. This includes during grocery trips: milk should be refrigerated promptly and never left in a warm car trunk.
Even if the milk looks and smells fine, it can still be unsafe if left out too long. According to the USDA, food left at unsafe temperatures can cause illness even without obvious signs of spoilage.
Risks of Drinking Expired Milk
The main concern with drinking expired milk is foodborne illness. “When milk spoils, microorganisms like bacteria have grown out of control in the milk,” says Labus. “Some of these organisms can cause gastroenteritis, others may just just make the milk smell or taste terrible.” Symptoms of gastroenteritis can include nausea, diarrhea and vomiting.
Another concern is unpleasant taste, smell and texture. “The primary risk is drinking a product that smells or tastes very bad and potentially experiencing a reaction to that,” explains Shumaker. Otherwise, pasteurized milk may still be safe a few days past the “best by” date if it smells and tastes normal.
That said, if you have any concerns that it’s unsafe to drink, it’s always best to avoid it.
Our Expert Take
The date that’s printed on your milk carton can give you an idea of how long it will be at its best quality, but it doesn’t tell you exactly when it will spoil. Usually, pasteurized milk can last a few days after the “best by” date if stored at safe temperatures. Milk that smells or tastes sour, or starts to curdle or change color, is likely spoiled.
However, appearance and smell aren’t always reliable indicators. Milk left at room temperature for more than two hours can still make you sick. If you’re unsure, it’s safest to toss it.
Read the original article on EatingWell
