Is it better to let leftovers cool down before putting them in the refrigerator?

This is wrong.

The correct approach is to put uneaten food into the refrigerator while it is still hot. The sooner the safer.

Because most bacteria grow and reproduce faster at 4℃~60℃, this temperature range is also called the "dangerous temperature zone" for food. When food is cooled, bacteria will take the opportunity to reproduce rapidly, and at room temperature, especially in the summer when the temperature is high, the reproduction rate of bacteria will increase exponentially.

The US Food and Drug Administration has recommended that both raw meat and cooked food should not be left at room temperature for more than 2 hours. If the room temperature exceeds 32°C, the storage time should be shortened to 1 hour.

Therefore, leftover food must be put into the refrigerator as soon as possible, the shorter the better. Every minute it stays at room temperature increases the danger.

Author: Zhong Yanping

Reviewer: Ruan Guangfeng, Director of Science and Technology Department, Kexin Food and Health Information Exchange Center