Reheating refrigerated leftovers can help save time and money, but some foods you should never reheat can cause food poisoning. Many people have the habit of keeping leftover foods in the refrigerator, reheating them the next day, and continuing to eat. However, this not only loses nutrients but also harms your health.

Some foods you should never reheat in the microwave may be at high risk of poisoning

1. What are foods you should never reheat in the microwave?

1.1 Foods you should never reheat – Rice

1.2 Foods you should never reheat – Eggs

Eggs are a rich source of protein. However, reheating eggs multiple times at high temperatures changes their protein structure and can make them toxic. Therefore, leftover eggs can be stored in the refrigerator for several days but must be reheated at a temperature of 74°C (165°F) or above before eating and reheated only once. Never use a microwave to heat eggs.

In particular, boiled and peach eggs should never be left at room temperature for too long. In addition to bacterial infections, the fats and proteins in eggs are denatured. So, reheating boiled eggs will break down the proteins that make them toxic and can harm your stomach and digestive system, such as vomiting and acute poisoning in severe cases.

1.3 Foods you should never reheat – Potatoes

When reheating cooked potatoes, their nutrients will be lost. Besides, high temperatures alter their chemical composition, creating harmful substances that can cause bloating and indigestion.

Moreover, if you eat greasy potato dishes, they cause damage to the gastrointestinal tract and even gastric reflux and stomach cancer.

In addition, reheating cooked potatoes can cause an increase in the amount of resistant starch, which is dangerous for people with diabetes.

1.4 Foods you should never reheat – Spinach

Spinach is so rich in nutrients, but it is not recommended to reheat it. During reheating, bacteria convert nitrates into nitrite and contribute to nitrosamine formation – potent carcinogens.

In addition, leaving the cooked vegetables for too long at room temperature will cause the amount of nitrite to rise, even up to 10 times after 12 hours. Therefore, after processing vegetables, eat them all at meals and do not eat the leftovers again.

1.5 Foods you should never reheat – Carrots

Like spinach, reheating carrots also increases nitrite and turns the nutrient-rich food into carcinogenic food. Therefore, you should not reheat the carrots to avoid damaging your health.

1.6 Poultry meat (Chicken, bird…)

Chicken and other poultry meats can be a source of salmonella transmission. This can be a big problem when reheating chicken in a microwave because heat waves will not be able to penetrate the entire chicken from the inside out.

Therefore, if chicken is contaminated with salmonella without being heated at high temperatures, it will not be able to destroy all bacteria and can lead to poisoning after eating.

Another reason for reheating chicken is often not recommended because it has a higher protein density than red meat – if reheated, the protein breaks down in different ways and can cause stomach discomfort.

However, if you still want to keep the leftover chicken for the next meal, put it in the refrigerator and maintain a temperature of 4°C (40°F).

It is best to use chicken within 1–2 days. When reheating, ensure the chicken should be heated to 74°C (165°F) or higher before eating.

1.7 Processed meat

Processed meats often contain chemicals and preservatives to extend shelf life, such as sausages, ham, bacon… Reheating them at high temperatures in the microwave can increase toxins, promote oxidative reactions, and increase cholesterol oxidation products (COPs) formation in processed meat. This contributes to food poisoning and cardiovascular diseases. So, processed meat is one of the foods you should never reheat in the microwave.

1.8 Mushrooms

Mushrooms contain a lot of vitamins and healthy nutrients. However, the protein content in the mushrooms is easily destroyed by other enzymes and microorganisms and transforms into toxins.

It is best to store mushrooms in the refrigerator for up to 24 hours before cooking or reheating at a temperature of 74°C (165°F) or above.

1.9 Celery

Celery has a lot of nutritional value, but this vegetable can become toxic if reheated. Moreover, celery contains nitrates that can convert into nitrites and contribute to nitrosamine formation. Therefore, you should never reheat celery dishes to avoid harm to your health.

1.10 White Radish

Like other vegetables, white radish also contains nitrates. So, repeated heating of vegetables at high temperatures contributes to toxins. White radish or beetroot should not be reheated to avoid the risk of food poisoning.

2. Why foods you should never reheat leftover food in the microwave

2.1 The temperature does not reach high enough

The main reason why reheating food in the microwave causes food poisoning is that the temperature does not reach high enough to kill bacteria.

So, if you take out the foods from the refrigerator or the food from outside temperature and then put them in the microwave, you must pay attention to adjust the perfect time, and the right temperature is 74°C (165°F) or higher, so that ensures that the food will heat all the way through.

If the food is not reheated at a sufficiently high temperature or non-uniform temperature distribution, the beams can not penetrate deep into the food. This makes bacteria grow and causes nausea, diarrhea, stomach pain, or life-threatening.

2.2 Using unsafe plastic containers

Not all plastic containers are safe to use in the microwave. If the plastic container contains harmful chemicals, this is a risk factor for your health because these chemicals can leach into foods from plastic containers.

For example, BPA from containers is absorbed into food and can cause diabetes, heart disease, and even infertility. It is best to use non-toxic glass and non-toxic ceramic.