In the refrigerator, at temperatures from +4 to +6, the processes of reproduction of microorganisms slow down dramatically, but do not stop completely.
Photo: Shutterstock.
Scientists from McGill University in Montreal claim that we have been storing ready-made food in the refrigerator incorrectly all our lives. They say that it is not necessary to cool the finished soup or stew in the kitchen, otherwise unnecessary bacteria will appear in it. It is better to send ready-made dishes directly to the refrigerator, while they are still hot. Is this really so and what are the safety rules for food prepared in the kitchen? Svetlana Sheveleva, Doctor of Medical Sciences, head of the Laboratory of Safety and Analysis of Nutrimicrobiomes of the Federal State Budgetary Institution “Federal Research Center of Nutrition and Biotechnology”, Komsomolskaya Pravda told.
Most likely, the Montreal researchers mean that it would be good to have refrigerators with a rapid cooling function (Super Cool, Power Cool). They are able to quickly cool even very hot food and this does not affect the temperature in the other compartments of the refrigerator in any way, our expert believes.
– We, food microbiologists, adhere to the following rule: already cooled food must be sent to the refrigerator. At least it was cooled to room temperature, says Svetlana Sheveleva.
If we store food in the refrigerator, even if it is packaged in portions, but still warm, then the temperature in the refrigerator compartment will start to change. To a greater or lesser extent, the entire refrigerator will heat up, which means that the storage temperature of those products that are already in it will also change.
Thus, we ourselves, unwittingly, create favorable conditions for the proliferation of harmful microbes, which do not even care about the cold.
– Unfortunately, these microorganisms also include pathogens, such as Listeria monocytogenes, which can cause a disease such as listeriosis. This is a foodborne infection, and the microbe that causes it can multiply at temperatures from +1 to – 10 degrees. If the temperature in the refrigerator fluctuates, we may face the fact that a person may become ill not from the product that he put in the warm refrigerator, but from the one that was stored there and will be stored there even after we have finished our food, we will already eat it,” says Svetlana Sheveleva.
TWO HOUR RULE
It is important to remember that any cooked food, whether it has been heat treated (frying, boiling, baking) or not, can be left at room temperature for no more than 2 hours.
“Immediately after cooking or baking food, microorganisms undergo a so-called thermal shock – of course, those that survived,” says our expert. “Then there is a lag phase – a period of time before the surviving microbes begin to multiply. As a rule, the lag phase lasts 3 to 8 hours. So, within two hours, we can say with a high degree of confidence that nothing bad will happen to the finished products cooling on the hob.
Unfortunately, there are small harmful microorganisms (spore-forming microorganisms, for example) that even benefit from heat treatment: they “like it hot.” Therefore, all cooking and kitchen hygiene rules, as well as the two-hour rule, must be strictly observed.
WHEN DOES THE TWO-HOUR RULE NOT WORK?
If you are preparing for the week, it is better to pack the ready-made borscht or stew in separate portions – containers. This way the product will cool down in 30-40 minutes and can be stored in the refrigerator.
IMPORTANT!
Food should be properly chilled. Soups and prepared main dishes should not be left open. This can lead to unnecessary bacteria being picked up from other products, such as unprocessed meat you will bring in or cook, from purchases from the store, etc.
It is therefore best to cover the dishes with a lid (with a slot to prevent condensation) or even with a clean kitchen towel, just like our grandmothers used to do. And leave to cool for 30-40 minutes.
After that, put it in the refrigerator, also observing the storage conditions.
Inside the refrigerator compartment, the temperature is distributed so that the coldest air will be at the bottom (+2) and the warmest at the top (+6, and sometimes +10 – +12) and at the refrigerator door (up to +10).
Food should be properly chilled. Soups and prepared main dishes should not be left open.
Photo: Shutterstock.
WHICH PRODUCTS ARE PARTICULARLY VULNERABLE TO MICROBES
– Meat. Raw – it should definitely go straight to the refrigerator or freezer. But you should also not keep fried food on the table for a long time. Especially if, as they say, it has blood on it or suddenly it was not fully cooked – not boiled, not fried. This is where a breeding ground for pathogenic bacteria, including E. coli, is located.
– Mixed salad, which contains both raw and cooked products. It is especially important here that, for example, Olivier is given boiled potatoes and chicken, but already cooled to room temperature. Otherwise, if they are put into the salad hot, together with other products and dressings, all this will create a pleasant microclimate for bacteria both in temperature and consistency.
– Rospotrebnadzor warns that Staphylococcus aureus likes to settle on cakes, pastries, meat salads and minced meat products. When these bacteria multiply, they release a toxic substance called enterotoxin, which causes gastroenteritis with severe poisoning.
Main symptoms: headache, nausea, repeated vomiting, sometimes fever and diarrhea.
STAY IN CONTACT
The safest temperature level in the kitchen for food is a temperature of +5 or less, i.e. a refrigerator, or +60 or more. i.e. an oven.
Meat, poultry and fish products can be stored in a closed container in the refrigerator for no more than one day. Up to 48 hours if thoroughly heat-treated.
Salads without dressing are stored for 24 hours. With the addition of sour cream, mayonnaise or vegetable oil – just a few hours!
Soups are the foods that last the longest in the refrigerator. They can be stored for up to 5 days, fish for up to 3. When they are heated properly (brought to a boil), the microorganisms they contain are destroyed.
KNOW
In the refrigerator, at temperatures of +4 to +6, the processes of reproduction of microorganisms slow down dramatically, but do not stop completely. There are also microorganisms that can reproduce in the refrigerator. These include E. coli, salmonella, listeria, campylobacter and Staphylococcus aureus itself.
