How to Tell If Food Has Gone Bad

The most important rule: do not taste it

It can be tempting to take a small bite or smell a container closely to decide if food is still good. That is not a safe test. Foodborne illness can be caused by harmful bacteria, viruses, parasites, or toxins that may not change the food’s appearance, smell, or taste.

Use the safer rule: if you are unsure about how the food was stored, how long it sat out, or whether it stayed cold enough, throw it out.

Common signs food may have spoiled

Some spoilage signs are easier to notice than others. These signs do not cover every possible risk, but they are strong warnings that food should not be eaten.

Why food can be unsafe without obvious signs

There is a difference between spoilage bacteria and illness-causing germs. Spoilage bacteria may make food smell bad, look strange, or feel slimy. But pathogenic germs that cause foodborne illness may not give you any warning signs.

This is why food safety guidance focuses so much on refrigerator temperature, cooking temperature, cross-contamination, and time limits. A food can pass the “smell test” and still be unsafe if it was left out too long or handled improperly.

Leftovers: when to throw them out

Most cooked leftovers are generally kept in the refrigerator for 3 to 4 days. After that, the safest choice is to throw them out or freeze them before they reach the end of that window.

Discard leftovers sooner if they were left out too long, stored in a warm refrigerator, touched with dirty utensils, or show mold, slime, off odors, bubbling, or unusual texture.

Do not scrape mold off cooked leftovers and eat the rest. Soft and moist foods can allow mold and bacteria to spread beyond what you can see.

Meat, poultry, and deli foods

Raw or cooked meat and poultry should be treated carefully because unsafe bacteria may not be visible. Throw away meat, poultry, bacon, sausage, or deli meat if it has a sour or unpleasant odor, sticky or slimy surface, gray-green discoloration with other spoilage signs, or an unsafe storage history.

For raw meat and poultry, time limits matter. Raw ground meats and poultry generally have short refrigerator windows. If you will not use them within the recommended time, freeze them while they are still fresh.

Seafood warning signs

Seafood can spoil quickly. Fresh fish and shellfish should smell mild, not sour, rancid, fishy, or ammonia-like. If a strong unpleasant odor becomes stronger after cooking, do not eat it.

Also discard seafood that is slimy, leaking, stored too warm, past its safe storage time, or has an unknown handling history.

Mold: what to keep and what to toss

The safest general practice is to discard moldy food, especially cooked foods, leftovers, soft fruits, bread, yogurt, sour cream, jams, soft cheeses, deli meats, hot dogs, bacon, and foods with high moisture content.

Some hard foods, such as hard cheese or firm fruits and vegetables, may sometimes be handled differently because mold does not spread as easily through dense food. However, this should be done carefully, following trusted guidance, and the safest choice for many households is still to discard the moldy food.

Do not sniff moldy food closely. Mold spores can irritate the respiratory system, and some molds may produce toxins under certain conditions.

Cans, jars, and packaged foods

Be especially cautious with canned or jarred foods. Throw away food from containers that are leaking, bulging, swollen, cracked, badly dented, spurting liquid, foamy when opened, moldy, discolored, or smell bad.

For home-canned foods, follow the warnings even more strictly. Do not taste home-canned food from a jar with a broken seal, bulging lid, leaks, spurting liquid, off odor, or unusual appearance.

Expiration dates are helpful, but not the only clue

Package dates can help with quality and planning, but they do not replace safe handling. Food can become unsafe before a date if it was left out, stored above safe temperatures, contaminated, or opened and kept too long.

Likewise, some foods may still look fine after a date but should not be eaten if they are perishable and have exceeded safe storage guidance. When dates, storage history, and food safety rules disagree, follow the safer rule.

Use time and temperature as your safety test

For perishable foods, time and temperature are often more reliable than smell. Bacteria can multiply quickly between 40°F and 140°F, often called the danger zone. Perishable foods should not sit out for more than 2 hours, or more than 1 hour when the temperature is above 90°F.

If your refrigerator loses power, keep the door closed as much as possible. If perishable refrigerated foods have been above 40°F for too long, they may need to be discarded even if they still look normal.

Simple decision checklist

1. Was it left out more than 2 hours, or more than 1 hour above 90°F?
2. Was it stored above 40°F or in an unknown temperature?
3. Has it been in the refrigerator longer than recommended?
4. Does it have mold, slime, off odor, swelling, leaking, or unusual texture?
5. Was the container damaged, bulging, cracked, or spurting liquid?
6. Are you unsure how it was handled?

If the answer to any of these is yes, the safest choice is to throw it out.

Bottom line

Food that has gone bad may show obvious signs like mold, slime, odor, discoloration, or damaged packaging. But unsafe food can also appear normal. The safest approach is to use storage time, temperature, and handling history first. When in doubt, throw it out.