When the odor from raw chicken makes you choke, or a leftover casserole is covered in fuzz, there’s no doubt that it’s time to throw them out. But what about the package of sliced turkey you opened a week ago, or the carton of milk with yesterday’s expiration date? How can you tell if that’s spoiled food in your fridge?

As food budgets get tighter, you may find yourself contemplating using leftovers that you used to send to the trash without much thought. This can be both good and bad, says Kelly A. O'Connor, registered dietitian and diabetes educator at Mercy Medical Center in Baltimore. On the one hand, we may be less wasteful, says O’Connor, who teaches a class on food safety. On the other, we may be taking chances with food that could be harboring illness-causing bacteria.

To conserve food and minimize your chances of food-borne illness, follow this use-or-toss guide:

FRUITS AND VEGETABLES

Use: Fresh vegetables that have been in the refrigerator less than the following times:

Green beans: two to three days

Corn and lettuce: one week

Carrots, celery and asparagus: two weeks

Garlic: two months

Onions, potatoes: four to six months

Toss: Any vegetables that have been in the refrigerator longer than the recommended times or show signs of spoilage, including garlic that has become soft or sprouted and greens such as kale or spinach that have become slimy.

Good advice: If outer lettuce leaves are slimy, remove the slimy leaves and use good ones underneath. Onions and potatoes that have sprouts are safe to use if they appear OK otherwise. Remove sprouts and prepare as usual. Some vegetables, including garlic, potatoes, sweet potatoes, onions and tomatoes stay fresher when stored outside the refrigerator.

FRESH MEAT AND POULTRY

Use: Meat purchased in past two or three days

Toss: Any meat that has not been cooked after three days; any meat with a strange appearance or smell

Good advice: If you are not going to use it within three days, cook or freeze. Meats can be frozen up to three months. Once cooked, meats will last another three days or more.

LUNCH MEATS AND HOT DOGS

Use: Unopened packaged meats up to their expiration date (or two weeks from purchase)

Toss: Any meat that has been opened for more than five days; any meat that has slime on it or has a strange smell

Good advice: If you won’t be using luncheon meats, hot dogs or bacon right away, they can be safely frozen for one or two months. Wrapping in individual portions will enable you to thaw just what you need.

CASSEROLES

Use: Any casseroles that have been in the refrigerator for less than a week as long as they don’t show signs of spoilage

Toss: Casseroles that have been prepared more than a week, or have an odor or mold 

Good advice: Label casseroles and other multi-ingredient dishes with the date you prepared them before placing them in the refrigerator. That way you won’t have to rely on memory to determine if they are safe to eat.

EGGS

Use: Eggs that are up to one or two weeks past the expiration date on the package. If there is no expiration date, use them up to four or five weeks after purchase.

Toss: Any eggs that are more than two weeks past the expiration date; eggs with even the tiniest cracks

Good advice: If eggs are past the expiration date, O'Connor recommends frying or scrambling them rather than using them in baked goods. Never wash eggs before storing. Doing so removes some of their protection against bacteria, she says.

MILK

Use: Milk that is up to two to four days beyond its expiration date

Toss: Milk that has been in your refrigerator more than four days past expiration date; any milk that smells bad, regardless of expiration date

Good advice: If you aren’t going to drink milk right away, store it unopened in the freezer for up to a month. Then, thaw, stir and use and as usual.

CHEESE

Use:

Hard cheeses (cheddar, Swiss, Parmesan): Unopened, follow expiration date; after opening, three to four weeks

Soft cheeses (cottage, brie): Unopened, follow expiration date; opened, one week.

Toss: Any soft cheese with mold

Good Advice: If hard cheeses have mold, you can cut off mold and safely use the rest.