Lasagna, shell gratin, tuna quiche… Out of habit or convenience, many of us let our dishes cool gently in the oven. Sometimes all night! The problem ? Bacteria love preparations left at room temperature for too long.
Meal leftovers: a breeding ground for bacteria
Notice to fans of batch cooking: when you cook a dish and want to enjoy it later, you should definitely not let it cool in the oven overnight.
In fact, “at room temperature, in the presence of water and nutrients from a food with an optimal composition (non-acidic, low in salt, etc.), a bacterial cell can divide into two daughter cells within about 20 minutes and thus give rise to considerable quantities of new cells“, recalls ANSES.
Under no circumstances should a dish be kept overnight at room temperature, under the pretext of waiting for it to cool before refrigeration.
The risk of food poisoning is real, confirms Dr Gérald Kierzek, medical director of True Medical. “Pathogenic bacteria proliferate quickly at room temperature, even in a cooked dish“, he admits.
When do germs start to develop?
A “danger zone” of between +8°C and +60°C exists, the emergency doctor further indicates.
“In general, the rule is not to leave a dish at room temperature for more than two hours before putting it in the refrigerator, because beyond that, bacterial growth explodes. In practice, a bacterial cell can double every 20 minutes in this context, making contamination exponential during the night. he reveals.
Little practical tip: if the quantity of food prepared is large (more than a liter or a kilogram), “it must be divided into smaller portions so that cooling is faster“, advises ANSES.
What good actions should you ultimately adopt in the kitchen?
Finding the balance between a dish that isn’t too hot (to the point of heating up the entire fridge) and a dish that doesn’t spend too much time at room temperature seems complex. And yet, it is possible, admits Dr. Gérald Kierzek. To do this, you just need to use common sense.
- Tip number 1: never wait all night to refrigerate a dish. As soon as it has cooled enough to not heat up the fridge, place it in the refrigerator, ideally within two hours;
- Tip number 2: to speed up cooling, divide the dish into small portions or use shallow containers;
- Tip number 3: never eat a dish that has remained at room temperature overnight, even if it has been covered or placed in the turned off oven;
- Tip number 4: control the temperature of your refrigerator (+4°C recommended) and place sensitive foods (meat, fish, ready meals) in the coldest zone;
- Tip number 5: throw away leftovers if in doubt: food poisoning can be serious, especially in children, pregnant women and the elderly.
In all cases, prevention requires speed and rigor. Better to refrigerate a lukewarm dish than to play Russian roulette with invisible but very much alive spores.