Rotten fish and meat gone bad. It smells gross, and it could make you really really sick.
Grace Choi is a chef instructor at New York University's Department of Food Studies. She gave INSIDE EDITION tips on how to tell when your food goes bad.
Tip one is pretty basic. You should keep fish, meat and chicken in your refrigerator no longer than 2 days. Choi demonstrated with a steak that was four days old.
"We have a clear comparison with fresh meat. You can see the discoloration. You can see the grain. If you eat this, you can get seriously bad food poisoning," said Choi.
Choi says cold cuts should be used within five days.
INSIDE EDITION's Megan Alexander asked, "What's the test for cold cuts? Can you see anything if they're bad? Will they smell?"
"You can definitely tell because they sort of have a glisten and when you touch it, it's very slimey," said Choi.
And here's something everyone can do. The key to keeping food fresh is to seal it in an airtight container. Choi put fruit and vegetables in Ziplock bags and then actually sucked all the air out.
Leftover take-out should also be transferred to an airtight container and eaten within three days.
Bread is best kept frozen, but never refrigerated.
Choi said, "If you want to keep bread for a long time, freeze it. It will last for two months. It captures the moisture in and take it out slice by slice if you want to toast it."
And here's a tip you might not know: Choi said store cottage cheese or sour cream upside down in your refrigerator. Doing so creates a vacuum that prevents the growth of bacteria.
Choi explained a simple way to tell if eggs are still fresh.
"On the large end there's a small air pocket. So when moisture is evaporated as the egg ages, the air pocket gets bigger. So if you're concerned about your eggs, use the water test. Put water into a bowl and put the egg on the bottom. If it's fresh, it will sink to the bottom. If it's bad, it will float," explained Choi.
Choi said milk will still be good up to five days after the date on the container, and organic milk will last even longer. But when in doubt, follow your nose.
"[If] milk says October 16th, do you have throw it out the next day?" asked Alexander.
"Actually, no. Because that's the pull date. That means that the grocer has to pull it from the shelves if it hasn't sold by that time. You have a grace period of about 5 - 7 days. If it starts smelling a little sour, a little rancid, throw it out. Trust your senses," said Choi.