Eating expired mozzarella cheese usually causes no harm if the cheese still looks, smells, and tastes normal. The date on the package is almost always a quality indicator, not a safety deadline. But if the cheese has actually spoiled, meaning bacteria have multiplied beyond safe levels, you could end up with food poisoning ranging from mild stomach upset to, in rare cases, a serious infection.
What matters isn’t the date on the label. It’s whether the cheese has genuinely gone bad.
What the Date on the Package Actually Means
Most people assume a “Use By” or “Sell By” date means food becomes dangerous the next day. That’s not how it works. The USDA is clear: a “Sell By” date tells the store how long to display the product for inventory purposes, and a “Use By” date indicates when the product is at peak quality. Neither is a safety date. In fact, except for infant formula, product dating isn’t even required by federal regulations in the United States.
This means mozzarella that’s a few days past its printed date can be perfectly fine, especially if it’s been consistently refrigerated. The real question is whether the cheese shows signs of spoilage.
How to Tell if Mozzarella Has Gone Bad
Your senses are more reliable than the printed date. Spoiled mozzarella gives off clear warning signs:
- Smell: Fresh mozzarella has a mild, milky scent. A sour, sharp, or rancid odor means the milk fats have broken down into compounds that taste as bad as they smell.
- Texture: A slimy or sticky surface is a sign of bacterial overgrowth. Fresh mozzarella stored in liquid may feel slightly slippery, but actual slime is different and unmistakable.
- Color: Pink, red, or brown patches indicate contamination by pigment-producing bacteria or yeasts, or oxidation. Normal mozzarella is white to pale yellow.
- Mold: Any visible mold on mozzarella, whether it’s fresh, shredded, or sliced, means you should throw it away entirely.
- Taste: If it tastes sharp, bitter, or “off” in any way, spit it out and discard the rest.
If none of these signs are present and the cheese has been properly refrigerated, eating it a few days past the date is generally safe.
Why You Can’t Just Cut the Mold Off
With hard cheeses like cheddar or parmesan, you can cut at least an inch around and below a mold spot and still eat the rest. Mozzarella doesn’t get that pass. The Mayo Clinic recommends discarding soft cheeses with any mold, along with any shredded or sliced cheese. Mold threads penetrate soft cheeses far deeper than what’s visible on the surface, and harmful bacteria like Listeria, Salmonella, and E. coli can grow alongside the mold even in areas that look clean.
Shelf Life Depends on the Type
Not all mozzarella spoils at the same rate. Fresh mozzarella, the soft kind packed in water or whey, is the most perishable. Once opened, it lasts only 3 to 5 days in the fridge. The liquid it sits in is a hospitable environment for bacteria once the seal is broken.
Low-moisture mozzarella, the firmer block or brick type commonly used for pizza, holds up much better. It can last up to two weeks after opening when stored properly. Pre-shredded mozzarella falls somewhere in between, lasting about 2 to 3 weeks after opening because the anti-caking agents mixed in help slow moisture buildup.
Unopened packages last longer than these windows, but once you’ve broken the seal, the clock starts ticking faster. Keep the cheese tightly wrapped or sealed in an airtight container.
Mild Food Poisoning Symptoms
If you eat mozzarella that’s genuinely spoiled, the most common result is a bout of food poisoning. Typical symptoms include diarrhea, stomach cramps, nausea, vomiting, and sometimes a low fever. For most healthy adults, this is unpleasant but self-limiting, meaning it resolves on its own within a day or two.
The bacteria most commonly associated with contaminated soft cheese include E. coli, Salmonella, Staphylococcus aureus, and Listeria. The first three tend to cause the standard gastrointestinal symptoms that most people think of as food poisoning. Staying hydrated is the most important thing you can do while your body clears the infection.
Symptoms that signal something more serious include bloody diarrhea, diarrhea lasting more than 3 days, a fever over 102°F, vomiting so frequent you can’t keep liquids down, and signs of dehydration like dizziness when standing, dry mouth, or very little urination.
The Listeria Risk With Soft Cheese
Listeria is the pathogen that makes spoiled soft cheese more dangerous than, say, spoiled bread. Unlike most foodborne bacteria, Listeria can grow at refrigerator temperatures, which means it can multiply even in properly stored cheese over time. And unlike typical food poisoning, listeriosis (the infection Listeria causes) can take up to two weeks to produce symptoms, so you might not connect your illness to a cheese you ate days ago.
In healthy adults, listeriosis may feel like a flu: fever, muscle aches, fatigue. But in vulnerable populations, it can turn life-threatening. It can enter the bloodstream and trigger sepsis, leading to organ damage. It can infect the nervous system, causing confusion, loss of balance, seizures, and hearing loss.
Pregnant women are especially at risk. A Listeria infection during pregnancy can lead to miscarriage, stillbirth, premature delivery, or a life-threatening infection in the newborn. Babies who survive severe listeriosis can develop lasting conditions including intellectual disabilities, paralysis, seizures, and blindness. People over 65 and anyone with a weakened immune system, whether from cancer treatment, diabetes, kidney or liver disease, HIV, or immunosuppressive medications, face similarly elevated risks.
For these groups, the margin for error with expired soft cheese is essentially zero. If there’s any doubt, discard it.
How to Store Mozzarella to Maximize Safety
Proper storage is the single biggest factor in whether your mozzarella stays safe past its printed date. Keep your refrigerator at or below 40°F. Fresh mozzarella should stay submerged in its original liquid and be used within a few days of opening. If the liquid turns cloudy or develops an off smell, the cheese is done.
Low-moisture and shredded mozzarella should be wrapped tightly or kept in a sealed bag with as much air squeezed out as possible. Every time you open the package and expose the cheese to air, you introduce new bacteria and moisture. If you know you won’t finish a block quickly, consider freezing portions. Frozen mozzarella loses some texture and becomes crumblier when thawed, but it’s perfectly safe and works well for cooking.
Cheese left out at room temperature for more than two hours enters the danger zone where bacteria multiply rapidly. If it’s been sitting on a counter or in a lunchbox for longer than that, treat it as suspect regardless of the date on the package.