The sight and smell of bad dairy products is easily recognizable, but what do they mean for your health? The sour (maybe even lumpy) milk (that you are forced to immediately spit into the sink), the mold growing on your favorite cheese (as you groan at the sight of the expensive and fresh gouda ruined). These are signs of the food going bad. Is it time to panic yet? No. Just like other foods, not all dairy products are created equal.
Dairy has a notoriously short lifespan. They are fresh foods that are prone to spoilage, but there is hope. In some cases you can even prolong the life of your favorite dairy products, but the longevity of your lactic libation can change depending upon when the carton was first opened, and how cold it was kept.
Bacteria grows in milk. Even after pasteurization, bacteria can grow. The best way to keep milk good is to store it in the coldest part of the fridge. The colder temperatures help to keep the bacteria growth in check. It doesn’t last forever, but it will prolong the life of the milk in your carton or jug.
How long does milk last?
Every time the door opens, it lets in warm air, and milk kept near the front of the refrigerator will turn bad more quickly. The same is true for milk that sits out for extended periods of time. Warmer temperatures mean more bacteria growth, which will sour the milk faster. And always be sure to close the carton tightly. This will prevent contamination and will protect against the milk absorbing bad smells from the fridge.
Note that the date on milk cartons is the sell by date, not the expiration or use by date. Generally, you have about 4–5 days after this date before the product goes bad if it was handled properly. Don’t worry about drinking milk that is past it’s sell by date by a few days. Unofficially (from personal experience), the milk will take on a slightly off, sweet taste before it goes sour. If you taste milk that is slightly sweet, you have about one day before it turns sour.
Cheese is tricky. Soft, fresh cheeses are not as hardy as hard or dry cheese. For example, fresh mozzarella is more susceptible to mold and spoilage than a harder aged cheddar.
If you see mold or notice an off smell with a fresh cheese, it’s time to throw it out. But most other cheese can take some mold and be just fine. If that block of cheddar you brought home has a little mold on the end, just cut off the moldy part and an additional ¼ inch, and you are good to eat the remaining portion. If you are buying bagged shredded cheese and you notice mold, it is possible to still use the cheese, if you can remove the molded portion – however, this is harder than it looks, and if there’s only a little left, you might be better off just throwing the bag away.
To make sure your cheese stays good as long as possible, wrap it in cheese paper. If you buy it from the store in plastic bag (different from a plastic container a fresh cheese may come in), remove it from the bag and wrap it in the cheese paper (parchment or wax will also work), then place it in a loosely sealed plastic container. This will allow the cheese to breathe and prevent mold from growing. Another tip is to store it in the vegetable drawer in the fridge: The higher humidity works in the cheese’s favor.
Is the sour cream supposed to look like that? Moldy is not good, but separated is just fine. It is normal for sour cream to separate out the liquid. Just mix it up again and you’re good to go. However, if the sour cream is moldy or off smelling, then it’s a no-go.
Sour cream can last as much as three weeks past the date on the container, whether it is opened or remains unopened, so long as it is in the refrigerator. But bits of food, like a touch of meat from the tacos, can easily find their way into the containers and promote bacteria growth. Bacteria like the proteins and sugars of the sour cream, and such cases the product can turn bad before the date is past.
Bottom Line: Use Your Senses!
When dealing with any kind of dairy, always trust your senses. Sour milk or barnyard smells are definite red flags. Slimy cheeses that shouldn’t be slimy and mold on fresh cheeses are also bad.
And of course, when in doubt, throw it out!