Thunderstorms swept across Michigan in the morning and evening on Tuesday, downing trees and power lines and leaving more than 365,000 residents without power.

When there is a power outage, many people first think of their refrigerator and several weeks’ worth of food supplies that are in danger of spoiling. This raises the question of which foods will have to be thrown away in the event of another power outage.

If the power was only out for a few hours and you didn’t open the fridge or freezer, the food is most likely fine. But if the power is out for a longer period of time, here’s how to store food safely and when to throw what out.

How to keep food safe

• Avoid opening the refrigerator and freezer doors to prevent cold air from escaping. According to the USDA’s Food Safety and Inspection Service, a refrigerator should keep food cold for four hours and a half-full freezer for 24 hours (48 hours if the freezer is full) if you don’t open the doors.

• If you know the power will be out for an extended period of time, stock up on ice or dry ice to keep food cold. According to the Food and Drug Administration, 50 pounds of dry ice will keep a 16-cubic-foot freezer cold for two days. Be careful when handling dry ice; do not touch it with bare hands and do not place it directly on food.

• Use a refrigerator-freezer thermometer to check the temperature.

• Food is safe in both the refrigerator and freezer if the temperature is 40 degrees or less.

• Food will stay fresh in the refrigerator for up to four hours. If the power is out for longer, place the food in a cooler and fill it with ice or frozen gel packs. You’ll need to make sure there’s enough ice to keep the food in the cooler at 40 degrees or below – and refill the ice if it starts to melt.

• Check the packaging. If the food still contains ice crystals or shows a temperature of 40 degrees or below when checked with a food thermometer, you can refreeze it, but the quality may not be the same.

• Group foods in the freezer to keep them cold longer.

• Store food in coolers on ice.

Food to throw away

Bacterial growth can develop in these foods that have been stored above 40 degrees for two hours or more. If your refrigerator has been without power for more than four hours, throw away the following:

• Raw, cooked or leftover meat, poultry, fish, soft cheese, milk, yogurt, eggs, leftovers, hot dogs, bacon, cold cuts, pizza, grated cheese, casseroles, pasta and pasta sauces, cut fruits and vegetables.

• Mixed salads such as tuna, chicken, potato and pasta salad.

• Cream-based salad dressings, sauces and soups.

• Opened mayonnaise, remoulade and horseradish, provided they have been stored for more than eight hours at temperatures above 50 degrees.

• Discard any food, such as bread or salad, that may have been contaminated by juices from raw meat, poultry or fish.

• Dips based on sour cream or other dairy products.

• Fruit and vegetables that have become slimy or spoiled.

• Throw away any food that has an unusual smell, color, or texture. Remember: if in doubt, throw it away and never taste food to see if it’s OK.

Food to be stored

• Condiments such as ketchup, mustard, jelly, jam, soy sauce and bottled marinade. These usually have high salt and sugar content, which can act as a preservative. Remember that jam and jelly can go moldy after three to four days. Throw away any products that show signs of mold.

• Butter/margarine.

• Hard cheese and processed cheese are usually fine.

• Foods that do not actually need to be refrigerated, such as fresh herbs, spices, flour and nuts.

• Fresh bread and rolls.

• Whole fruits and vegetables that show no signs of spoilage.

How to clean

Once power is restored, here’s how to care for the inside of your refrigerator or freezer and eliminate odors.

• Discard spoiled or questionable food.

• Remove shelves, crispers, and ice trays. Wash thoroughly with hot water and dish soap. Then rinse with a disinfectant solution of 1 tablespoon unscented liquid chlorine bleach per gallon of drinking water.

• Wash the inside of the refrigerator and freezer, including the door and seals, with hot water and baking soda. Rinse with a disinfectant solution.

• Leave the door open for about 15 minutes.

What to do if the smell is still there?

• Wipe the inside of the appliance with equal parts vinegar and water to destroy mold.

• Leave the door open for several days to air it out.

• Fill the refrigerator and freezer with rolled up newspapers. Keep the door closed for several days. Remove the newspaper and clean it with vinegar and water.

• Sprinkle fresh coffee grounds or baking soda loosely into a large, shallow container on the bottom of the machine.

• Use a commercial product available at hardware and home supply stores. Follow the manufacturer’s directions.

The U.S. Department of Agriculture Meat and Poultry Hotline (888-674-6854) is open weekdays from 10 a.m. to 6 p.m. Recorded food safety alerts are available 24 hours a day. For more information, visit fsis.usda.gov.

Detroit Free Press food and restaurant writer Susan Selasky contributed to this article.

This article originally appeared in the Detroit Free Press: How long does food last during a power outage? What you should know