Reheating rice can be problematic because it may harbor spores of Bacillus cereus, a bacterium that can cause food poisoning. These spores can survive the cooking process, and if rice is left at room temperature too long before refrigeration, the spores can grow into bacteria that will multiply and may produce toxins that survive reheating.
Reheating chicken in a microwave can sometimes unevenly heat the meat, leading to certain parts being hot enough to allow bacteria growth. It’s safer to reheat chicken to a high temperature throughout to kill any potential bacteria.
Cooked potatoes that are left to cool at room temperature and not properly stored can provide the right conditions for the growth of botulism bacteria. Reheating them won't always kill these bacteria, so it's best to store them in the refrigerator immediately after cooking.
These vegetables are high in nitrates, which can turn into nitrites and then into nitrosamines, some of which are known carcinogens, when reheated. It’s generally safer to eat them freshly cooked.
Eggs and dishes containing eggs should be thoroughly cooked the first time because partial cooking and then reheating can increase the risk of bacterial growth and food poisoning.
High in proteins and beneficial nutrients, mushrooms also deteriorate rapidly. Reheating mushrooms can change their protein composition and potentially cause digestive distress.
Reheating seafood often leads to overcooking it, which can make it rubbery and unappetizing. More importantly, if seafood wasn't refrigerated promptly or reheated properly to the right temperature, there's a risk of food poisoning from bacteria like Salmonella or E. coli.
Similar to spinach, beets are also high in nitrates. Reheating beets can be harmful as it can promote the conversion of nitrates to nitrites, which are potentially carcinogenic.