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.
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.
Rotisserie chicken loses moisture as it cools, which is why it should be consumed immediately, when it’s most palatable.
Mushrooms are delicate and, if not cooked and stored properly, can deteriorate and cause an upset stomach.
Potatoes can contain Clostridium botulinum, the bacteria that causes botulism, a potentially deadly form of food poisoning.
Beets are rich in nitrates, which break down into nitrites if overprocessed through reheating.
Ideally, rice should be consumed immediately after cooking. Raw rice may contain spores of a bacterium called Bacillus cereus.