1. Leftovers 18 hours.

After 18 hours, the experimenter took out four plates marked "18 hours" from the refrigerator and put them in the microwave oven for heating and testing. The results showed that the nitrite content in stir-fried dishes increased significantly, by 43% compared with 6 hours, by 54% in braised crucian carp and by 47% in scrambled eggs with leeks, while the nitrite content in braised pork did not change much.

It can be seen from this experiment that the nitrite content of stir-fried dishes, braised pork and braised crucian carp exceeded the national standard after overnight dishes were put at noon the next day.

2. Leave the leftovers for 24 hours

Almost 24 hours after the four dishes were cooked, the experimenter took out the last batch of four dishes marked "24 hours" from the refrigerator and put them in the microwave oven for heating and testing. The results showed that compared with 18 hours, the nitrite content of the four dishes continued to increase significantly, and all of them exceeded the limit standard of "Limits of Pollutants in Food".