Uncooked rice can contain spores of a bacteria that causes food poisoning, called Bacillus cereus. This harmful bacteria is able to survive throughout the cooking process and if the leftovers aren’t stored properly, it will spread and multiply, producing toxins that cause vomiting and diarrhea. The reheating doesn’t really help, because the spores of the bacteria can survive even boiling hot temperatures.
Ideally, you should serve rice right after it has been cooked, but if that’s impossible, place it in the fridge or freezer as soon as possible (within one hour) and consume it in the next 24 hours. When you reheat rice, make sure that the dish is steaming hot and do not reheat it more than once. Also, never leave cooked rice at room temperature for more than one hour – the bacteria spreads quickly.
2. Green vegetables
Nitrate is a mixture of nitrogen and oxygen that exists in minerals, soil, ground water and the atmosphere. Plants absorb it from the soil, and it’s also commonly found in fertilizers. All vegetables contains some amount of nitrate, but green veggies like spinach, celery, lettuce, collard greens and cabbage contain the highest amounts.
Nitrate is not dangerous for the human health by itself, but when digested, the body converts it to nitrite, a metabolite of nitrate that has been known to cause methemoglobinemia, a condition characterized by headaches, fatigue and seizures. Nitrite interacts with other substances in the body to create cancer-causing compounds and it also damages hemoglobin’s ability to carry oxygen to the cells, which is especially dangerous for infants.
Although the process of cooking eliminates a significant amount of the nitrite in vegetables, when cooked veggies are left at room temperature for too long the bacterial processes will cause a greater accumulation of harmful nitrite. So actually it’s all about the way you store them – if you plan on consuming the leftovers of cooked vegetables during the next 12 hours, make sure to store them in your fridge, and if you plan to keep them stored for longer than 12 hours, the best option is to freeze them.
3. Vegetable oil
Repeatedly heating up polyunsaturated oils that contain linoleic acid, such as corn, soybean and sunflower oils, may release a toxic compound derived from fatty acids that’s called 4-hydroxy-trans-2-nonenal.
A big number of studies have associated the consumption of this toxin with serious health problems such as cardiovascular disease, Parkinson’s, Alzheimer’s, Huntington’s disease and cancer. Heating this kind of vegetable oils for too long can cause the same effect. In order to prevent this, never heat any oil to the point of smoking and make sure to use it only once.
If you leave your cooked potatoes to cool down at room temperature for an extended period of time instead of placing them in the fridge as soon as you finish your meal, they will lose almost all of their nutritional value and the growth of harmful bacteria will be encouraged. More specifically, the temperature can cause the growth of a rare bacteria called Clostridium botulinum, which cannot be eliminated by reheating them later.
This bacteria is responsible for causing botulism, a fatal condition that’s considered a medical emergency. Make sure you refrigerate potatoes as soon as possible to make sure they’re safe to eat and don’t reheat them to avoid increasing the amount of any toxins they may contain.