In daily life, we often have leftover food. Many people believe that putting hot food directly into the refrigerator will overload it or even shorten its lifespan, so they wait for the food to cool completely before refrigerating. However, this practice is actually not scientifically sound. From a health perspective, the process of cooling food slowly can pose various risks, making the correct storage method very important.

Putting Hot Food into the Fridge Won’t Damage It:

Many worry that placing hot food in the fridge will cause the appliance to work harder and reduce its lifespan, but this concern lacks scientific basis. Modern refrigerators use inverter compressor technology that can effectively regulate temperature. Even if you put food at 60°C inside, the fridge’s internal temperature only fluctuates slightly—by about 2–3°C—and typically returns to normal within 30 minutes. Therefore, fears about damaging the fridge by storing hot food are unfounded.

Risks of Waiting Until Food is Completely Cool:

From a food safety standpoint, waiting for leftovers to cool down completely before refrigeration is very risky. As food cools at room temperature, it provides ideal conditions for bacterial growth. This risk increases in warmer weather, as heat accelerates the process. The World Health Organization (WHO) defines the range between 4°C and 60°C as the “danger zone,” where pathogens like Salmonella and Staphylococcus aureus can quickly proliferate. Slow cooling allows bacteria ample time to multiply, increasing the risk of spoilage and food poisoning.

For example, chicken soup initially at 60°C left at 25°C room temperature for 3 hours may still have a core temperature of 42°C. During this time, bacteria can increase 64-fold! More alarmingly, some bacteria can produce heat-resistant toxins at 30°C, which cannot be destroyed even by reheating, greatly increasing the risk to food safety.

How to Properly Cool Food?

To effectively prevent bacterial growth, it’s important to cool food quickly through the danger zone and bring the temperature down below 7°C as soon as possible. Studies show that putting a large pot of hot soup directly into the fridge can take up to 6 hours to cool safely. However, dividing the food into shallow containers and using an ice-water bath can reduce this time to about 45 minutes. Here are some practical tips for home food storage:

1. The 2-Hour Rule: Refrigerate cooked food within 4 hours; if the room temperature exceeds 32°C, reduce this to 1 hour.

2. Smart Portioning: Divide food into portions no thicker than 4 cm, using stainless steel or glass shallow containers for faster cooling. Cut meat into pieces around 100 grams.

3. Sealing Techniques: Use airtight containers or vacuum sealers rather than plastic wrap or loosely covered bowls. Vacuum sealing soups can prevent air exposure.

4. Precise Temperature Control: Store leftovers on the back wall of the fridge where it is coldest. Try not to store food on the fridge door shelves, as the temperature there varies more and can cause food to spoil quicker.

Additional Storage Tips:

While refrigeration slows down food spoilage, it doesn’t preserve food indefinitely. Different foods have varying safe refrigeration times. For example, rice and noodles can reach harmful levels of Bacillus cereus after 24 hours; leafy greens can accumulate 37% more nitrites after 12 hours; fish and soy products can only inhibit about 70% of microbial activity even at 5°C. Therefore, to ensure freshness and safety, it’s best to consume leftovers within a short time frame.