How did we develop the use of cold to preserve food?
Cold has been used on a wide scale for preserving food since the 19th century.
Cold plays a key role in long-distance transportation, making food produced in other regions of the world, such as fresh fruit and vegetables, dairy products and meat, more widely available.

    

The first railway wagons cooled using natural ice appeared in the United States in 1880. Techniques for making artificial cold developed very quickly. Such techniques use air, water or gas such as ammonia to produce cold.

What is the difference between freezing and deep-freezing?
Deep-freezing reduces the temperature of food rapidly, whereas freezing does not. The resultant ice crystals are finer and so food retains its texture and flavour.

What is the cold chain?
The cold chain refers to the steps that must be carried out to produce frozen food, such as packaging, transportation and storage. To maintain the quality of frozen food, it must be stored at a temperature of minus 18°C or lower throughout its journey from the factory to our home freezers. Respecting the cold chain prevents bacteria from developing.

Why should we never refreeze food?
If we refreeze food that has thawed or been defrosted, we are breaking the cold chain and bacteria will develop very quickly. This can pose a health risk, as the bacteria are likely to cause food poisoning. This is what happens with salmonella, staphylococcus and listeria. These bacteria may be fatal for babies, pregnant women, and sick or elderly people.