- Plain rice
- Anything that’s already been reheated
- Spring rolls
- Keep these tips in mind
- Clams, mussels, oysters
- Plain rice
- Spinach and lettuce
- Processed meats
- Leftovers more than three days old
- Anything left at room temperature for more than two hours
- Anything that smells off
Everyone seems to be meal-prepping these days, and for good reason. Preparing or partially preparing meals in advance can save you time and money and even be fantastic for your health. However, whether you’re reheating something you “prepped” earlier in the week or last night’s restaurant leftovers, it’s important to remember that there are some foods you should never reheat.
Anything that’s already been reheated
Technically, most food can be safely reheated multiple times as long as its interior temperature gets hot enough to kill bacteria, but the more times you reheat something, the greater the chance of it not being properly heated all the way through. Unless you consistently use a food thermometer while cooking, it’s best to err on the side of caution and not reheat leftovers that have already been reheated once.
Reheating cooking oil (or deep-fried food) could be potentially hazardous. The trans-fat content of frying oil increases each time the oil is reheated.
While you’ll likely want to avoid reheating deep-fried spring rolls for health reasons, there are also taste-related reasons for not doing so. A spring roll’s multiple layers make it very difficult to recreate its crunchy texture once it’s been cooked and allowed to cool.
Keep these tips in mind
Breast milk should never be reheated in a microwave. Not only can reheated breast milk become less nutritious, it may also pose a risk to infants.
Eggs may contain bacteria, called Salmonella enteritidis, which can cause food poisoning. They may hold up to a second reheating in some cases, but as a potentially hazardous food, it may not be worth the risk. Cooked eggs that have been left at room temperature for more than two hours should be thrown out.
Rotisserie chicken loses moisture as it cools, which is why it should be consumed immediately, when it’s most palatable. As for chicken cooked in other ways, be aware that chicken is a potentially hazardous food that can contain Salmonella. Heating and reheating it can increase the risk of cooking error and food poisoning. Whatever you do, don’t use a microwave to reheat chicken.
Clams, mussels, oysters
Shellfish, such as clams, mussels, oysters and scallops, is a potentially hazardous food and can carry bacteria that cause food poisoning. Handle such food with care during storage and cooking. Most bivalve shellfish are safest to eat immediately after being appropriately cooked.
Mushrooms are delicate and, if not cooked and stored properly, can deteriorate and cause an upset stomach. If you’re eyeing mushrooms that were cooked over 24 hours ago, do not reheat them.
Cooked potatoes that sit at room temperature after cooking should not be reheated. Potatoes can contain Clostridium botulinum, the bacteria that causes botulism, a potentially deadly form of food poisoning. These bacteria can proliferate at room temperature, so it’s best to eat potatoes immediately after cooking or cool them down promptly for cold dishes like potato salad.
Beets are rich in nitrates, which break down into nitrites if overprocessed through reheating. Consumed fresh or immediately after cooking, beets are a wonderfully healthy food, but it’s best to avoid reheating them.
There is some controversy over how harmful nitrites really are, but some doctors believe them to be carcinogenic. For now, it may be best to err on the side of caution and consume nitrate-rich food in a state as close to fresh as possible.
Ideally, rice should be consumed immediately after cooking. Raw rice may contain spores of a bacterium called Bacillus cereus, which can cause food poisoning. The longer cooked rice is left sitting at room temperature, the higher the chance that these spores (which can survive the cooking process) will develop into bacteria and multiply.
A creamy risotto can quickly go sour in the fridge. When cooking, adjust portions appropriately so that you cook only what you need and avoid leftovers.
As with beets, celery contains naturally occurring nitrites that can become toxic if reheated.
Turnips are also high in nitrites and should be cooked only once.
Spinach and lettuce
Spinach and lettuce are both high in nitrates. If you’re concerned about those nitrates becoming nitrites, avoid reheating these leafy greens. Eat them raw or immediately after cooking.
Microwaving processed meats increases their volume of cholesterol oxidation products, which can damage your cardiovascular health.
Leftovers more than three days old
Toss out anything in your fridge that’s more than two to three days old—it’s not worth the risk of food poisoning. If you want to keep leftovers for longer, pop them in the freezer.
Anything left at room temperature for more than two hours
Has your food been sitting at room temperature for more than two hours? If it has, throw it out.
Reheating cold coffee in the microwave will leave it tasting acidic and stale.
Anything that smells off
This one goes without saying. Don’t reheat (or eat!) anything that smells like it’s gone bad.