At room temperature, vegetables that produce more nitrite by the next day include spinach, cauliflower, green beans, cabbage, and green bell peppers, with spinach containing far more nitrite than other vegetables. Vegetables that produce less nitrite include tomatoes, lettuce, chives, zucchini, eggplant, garlic stalks, carrots, and celery. Experts recommend that fresh vegetables should be cooked and eaten as soon as possible. If there are leftovers, they can be stored at low temperatures (such as in a refrigerator), but not for too long.
When dining out, people often bring unfinished food home, but leftovers should not be stored for too long. Wang Wenfang from the Institute of Nutrition and Food Safety at the Chinese Center for Disease Control and Prevention reminds people that leftovers can produce nitrite after being salted for a long time, especially some leafy green vegetables, with Chinese cabbage being the most prominent. Nitrite can cause food poisoning. When it enters the human body, it can react to form nitrosamine, a carcinogenic substance.
Experiments have shown that various vegetables, after being heated and then left to stand, contain nitrite to varying degrees. The longer they are left, the higher the nitrite content. However, storing them at low temperatures results in much less nitrite than storing them at room temperature. Winter-stored Chinese cabbage and potatoes contain nitrite immediately after being stewed without being left to stand. After being stored at room temperature overnight for a day, the content is even higher, far exceeding that of other vegetables.
According to relevant data, 8 out of 10 food poisoning incidents are related to nitrite. To reduce the intake of nitrite from leftovers, Ma Zhaohui, Deputy Section Chief of the First Section of Health Supervision at the Beijing Health Supervision Institute, offers the following advice on how to store and consume packed leftovers:
Store leftovers separately in clean, airtight containers to avoid cross-contamination. Leftovers should be eaten within 5-6 hours if possible. Cold dishes are prone to bacterial growth and should not be packed. Fish should be reheated for only 4-5 minutes to avoid excessive loss of nutrients. When reheating meat, add a little vinegar, which not only enhances its nutritional value but also aids in human absorption. Starchy foods should be consumed within 4 hours, otherwise, parasitic staphylococci cannot be broken down even at high temperatures.
In addition, when eating leftovers, one should consume more foods that inhibit the formation of nitrosamine. For example, allicin in garlic can inhibit nitrate-reducing bacteria in the stomach, significantly lowering nitrite levels in the stomach. Tea polyphenols in tea can block the formation of nitrosamine. Foods rich in vitamin C can prevent the formation of nitrosamine in the stomach and also have a mutagenic inhibitory effect on nitrosamine.