What should you cover food with?

Food is not covered while it is still boiling hot; it is covered once it has cooled down, and it goes into the fridge that way. What you cover it with is decided by the food itself: a lidded container, cling film and aluminum foil are made for different jobs, and what is right for one is not right for another.

What does covering food do?

Its first job is to prevent contamination. TÜBER, Türkiye's national dietary guideline, says that in cold storage raw and cooked foods should be kept on separate shelves, with cooked foods placed on the shelf above raw ones and kept covered. Standing on the upper shelf prevents dripping, and being covered prevents transfer by touch and splashing.

Its second job is to stop drying and the exchange of smells. Food left uncovered loses water from its surface and takes on the other smells in the fridge; the reason it is left on the plate the next day is usually not spoilage but these two changes. The same guideline also asks that foods to be frozen be kept in covered containers.

When do you cover it?

The guideline says that hot dishes should not be put straight into the cooler, and that dishes as they cool should be covered and kept in the refrigerator. It gives a target for the cooling too: the temperature of the food should be brought down from 60 °C to 37 °C in no more than two hours, and from 37 °C to 4 °C in no more than four hours. Cooling large amounts quickly by moving them into shallow containers no more than 10 centimeters deep is recommended in the same place.

There is a second limit in the same section: cooked dishes should not be left at room temperature, on the counter or on the stove, for more than two hours. The right moment to cover falls between these two sentences. A container covered while boiling hot holds the steam inside and slows the cooling; waiting for it to cool completely pushes the two-hour limit. In practice this means leaving it uncovered until it reaches a temperature your hand can stand, then covering it and putting it in the fridge.

Where do a lidded container, cling film and foil each go?

A lidded container is the most leakproof of the three; it holds smells in both directions, stacks and is reusable. Cling film works for covering the mouth of a straight-sided container for a short time, but it does not hold well on an irregular container or on a pot. Foil blocks light and stands up to oven temperature; on the other hand it lets air in at the edges, which means it is not enough on its own for long storage.

Foil has a limit set by regulation as well. The Türk Gıda Kodeksi (Turkish Food Codex) regulation on materials and articles in contact with food requires that the label of uncoated aluminum and aluminum alloy products carry one of the following statements: "do not use for storing, cooking or processing foods that are acidic (pH < 4.5), alkaline (pH > 8.5) or have a salt content above 3.5% NaCl", or "use only for storage under refrigerator conditions". In other words, covering items such as tomato sauce, a dish with lemon in it or something in brine with foil is a use the product's own label warns against. The same regulation also states that zinc and galvanized materials cannot be used for acidic foods.

The practical rule that comes out of this is short: a lidded container for acidic, salty or long-waiting food; foil for what goes into the oven or needs protection from light; film for a short wait in a straight-sided container. When you are not sure, looking at the use information on the box is the shortest way; that information is required to be on the label.

What about food that will wait on the table?

For a dish that will wait a short time on the table or the counter, the pot's own lid is enough; there is no need to use anything else. Covering one plate with another plate does the same job and makes stacking in the fridge easier.

For dishes served hot, the guideline has a separate limit: hot dishes should be held for no more than two hours below 63 °C, and cold dishes for no more than four hours above 8 °C. At a crowded table this limit is what decides how long the food stays out; covering it holds the temperature for a while but does not extend that period.

What can you do today?

You can check whether the lids of the two or three storage containers you use most are really leakproof; film used in place of a container with a worn lid usually does not do the same job. Setting aside a single glass container for acidic dishes saves you thinking every time about what to cover them with. And after dinner, leaving the container on the counter for a short while to cool rather than putting it straight into the fridge lets you cover it without pushing the two-hour limit.