interviewee: Zhai Fengying, deputy director of nutrition and Food Safety Institute of China Center for Disease Control and prevention, and executive vice president of China Nutrition Society. One of the major themes of


is “eating”. Most people still have the habit of preparing snacks. But now people have enough “oil and water” in their stomachs and can’t eat big fish and meat. So after the festival, many families will be filled with leftovers such as stewed meat, ribs, steamed bread, dumplings and so on. Is this leftover food harmful to your health? How to deal with it? What can be saved? How to make it healthy and delicious? In response to the above questions, we interviewed Zhai Fengying, deputy director of Institute for nutrition and food safety of China Center for Disease Control and prevention, and executive vice president of China Nutrition Society, and asked her to answer questions about leftovers.

life times: is eating leftovers harmful to health?

Zhai Fengying: we have always advocated “how much to eat, how much to cook”, and try not to leave the food left over, mainly because there are three major health risks in leftovers. One is the loss of nutrition. For example, the vitamin C in vegetables is afraid of heat, and it has lost 30% ~ 40% when stir fried for the first time. If it is reheated again, the content of vitamin C will be less. Vitamin E, folic acid and so on are the same. Second, meat and bean products are high in protein content, which are favored by microorganisms and easy to breed bacteria. Third, leftovers may produce carcinogens, we often say nitrite is a carcinogen.


life times: many people know that nitrite is a carcinogen. What kind of food is most likely to produce nitrite?

Zhai Fengying: Vegetable leftovers are more prone to this problem. Vegetables absorb nitrogen from the soil, store it in the form of nitrate, and then synthesize amino acids and proteins. Dark green leafy vegetables usually contain the highest nitrate content, such as spinach, rape, leek and so on. Nitrate in vegetables is slowly reduced to nitrite by bacteria, and nitrite is the highest in long-standing leftovers. Under normal conditions, nitrite in the diet will not cause harm to human body, but if excessive intake, nitrite will produce excessive nitrosamines in the acidic environment of the stomach, which may induce cancer. When cooked vegetables are placed at a higher temperature for a period of time, the content of nitrite will increase. Bacteria can also be eliminated by high temperature. If nitrite is produced in food, it can’t be eliminated even by reheating.

life times: which leftovers are prone to bacteria?

Zhai Fengying: all kinds of leftovers are easy to breed bacteria, which is closely related to temperature. In the heating room in winter, the temperature is suitable for the growth of microorganisms. It is better not to leave the leftovers outside for too long. Seafood, meat, bean products have high protein content and high water content, which are suitable for microbial growth. It is best to eat them on the same day or put them into the refrigerator in time after cooling. The remaining dumplings, steamed buns, etc. should also be put into the refrigerator in time. Steamed bread should be stored in the freezer or freezer, and should not be exposed to the air.

life times: how to save leftovers? Zhai Fengying:

Zhai Fengying: the principle of preserving leftovers is to wrap the leftovers in fresh-keeping boxes, bags and other clean containers, and put them into the refrigerator immediately. Don’t keep them for too long at room temperature. The emphasis here is to cool thoroughly, because hot food entering the low-temperature environment will cause steam condensation, promote mold growth, and cause other food in the refrigerator to mildew. The leftovers placed at room temperature should be finished in five or six hours.

life times: which leftovers must be thrown away? What can I keep? Zhai Fengying:

: first of all, vegetables should not be preserved, especially green leafy vegetables, which not only have high nitrite content, but also have lost the most valuable vitamins. However, generally speaking, the closer to the root, the lower the content of nitrite, so beans, cucumbers, tomatoes, onions and other vegetables can be properly left, but it is best to eat them when they are returned to the pot for the second time. Secondly, seafood emphasizes freshness. After the rest, it is not only flavor free, but also easy to breed bacteria. It is better to eat it at one meal. Finally, steamed stuffed buns, dumplings and other starchy foods with stuffing are easy to breed Staphylococcus and aflatoxin, which can’t be killed under high temperature. It’s better to eat them in one or two days.


can leave food: coarse grain, beans, because of their mineral and dietary fiber is particularly rich, reheating again also has nutritional value; steamed bread, rolls and cakes can be put into the frozen layer, generally can be stored for about a week; meat can be divided into small parts, put into the refrigerator in time, and then take out a small box each time to avoid repeated heating.

life times: what should we pay attention to when the leftovers are returned to the pot? How can we make leftovers “renovated” and eat healthier?

Zhai Fengying: the leftovers must be returned to the pot at high temperature before eating to completely kill the bacteria. The so-called “heat through” refers to heating the whole dish to 100 ℃ and keeping the water in the steamer boiling for more than 3 minutes. This also suggests that cold dishes, regardless of meat and vegetable, should not be left, because bacteria are not easy to be killed without heating.


have their own skills in heating different leftovers. Meat is usually heated for more than 10 minutes or microwave for more than 1 minute. Fish can be returned to the pot together with onion, ginger, garlic, cooking wine and vinegar, which not only helps to kill bacteria, but also improves freshness.


leftovers are often sold and taste bad, so we can use some small skills to “renovate”. For example, sauce beef, stewed ribs with green onions, garlic, or with potatoes, beans and other stews. Rice can be cooked porridge, fried rice, or cooked meat. Dumplings and steamed bread can be fried. ▲

Leave a Comment