Most of us take the humble fridge for granted but it is an invention which had a huge impact on the modern world
Most of us take the humble fridge for granted. But it is an invention which had a huge impact on the modern world, radically improving our nutrition, our way of life and even opening up more places for mankind to live.
Bacteria are present in all food. At room temperature they multiply rapidly, making food inedible and even dangerous.
In cold temperatures, bacterial activity slows dramatically. At freezing point or below, it stops. So keeping food cold can maintain its freshness for days when it might otherwise last only hours. Freezing can preserve it for months or years.
Centuries later people were still keeping food outside, for example in window boxes or storage tins buried in the ground. It was not very efficient but it was better than nothing. Even so, eating spoiled food was a common cause of illness and even death, especially in summer.
In some countries an ice industry sprang up, with ice harvested from frozen lakes and transported large distances, melting as it did so, before delivery to cities and even individual homes. With luck it would keep food fresh for two days in an "ice box".
Buying ice was expensive. Country estates might have had ice houses, but most ordinary people had no such luxury. Their food was bought and eaten the same day and they shopped daily. Milk was delivered each morning and had to be drunk that day. The food was all grown locally. Local meat was bought, freshly-slaughtered, from local butchers.
Some food could be preserved by methods such as drying, pickling or smoking, but that was only suitable for a small range of produce.
Artificial refrigeration — making an enclosed space cooler by removing heat - was the key breakthrough. It works like this:
If you rub alcohol on your skin, your skin will feel cold. That's because alcohol evaporates at room temperature and as it does so it draws heat from your body. The great American "founding father" and inventor Benjamin Franklin proved this with an influential experiment in the 1750s. He repeatedly dabbed the solvent ether on to the bulb of a thermometer and let it evaporate each time, blasting it with a bellows to speed it up. The thermometer's temperature fell way below freezing -- as the evaporation drew heat from the bulb. (Franklin speculated that using this principle it would be possible "to freeze a man to death on a warm summer's day" — a prescient prediction in 1758 of air conditioning).
A similar reaction occurs in a fridge. A "refrigerant" gas is forced, by compression, to condense into liquid and then evaporate back into gas. As it does so it draws heat from inside the machine and makes it cooler. This cycle repeats again and again, so the fridge is kept constantly cold.
As early as 1756, Scottish doctor William Cullen created a small amount of ice by making the solvent ether boil away into gas, absorbing heat as it did so. This was just an experiment, though . . . there was no way of using the method practically.
Almost half a century later, in 1805, American inventor Oliver Evans took that basic principle and drew up the design for a fridge based on compressing gas, though it was never built. It fell to another American inventor, Jacob Perkins, to build a machine from Evans' idea, filing a patent in 1834 for "an apparatus and means for producing ice, and in cooling fluids".
His machine was not very practical and, up against a thriving American ice industry, was largely ignored.
The man credited with developing the first actual "fridge" was an American doctor, John Gorrie, who built an ice-maker in 1844 based on Evans' work of decades earlier. He also pioneered air conditioning at the same time, since his idea was to blow air across the ice-making machine to cool hospital patients suffering from malaria in Florida.
Gorrie did not make the fortune he deserved. His business partner died and his leaky machines were mocked by the Press and the ice-producing firms to whom he could have been a threat. He died sick and broke aged 51.
In 1856 another American, Alexander Twinning, began selling a fridge based on compressing gas. An Australian, James Harrison, made a bigger version for brewers and meat-packers trying to keep their beer and beef cold in the sweltering heat Down Under.
Manufacturing of fridges really became a reality in the 1870s when a German professor, Carl von Linde, developed a reliable mechanism by which the machines would liquefy gases — ammonia being the coolant of choice.
It still took another 40 years, around the end of World War One, before fridges were being mass produced and cheap enough for ordinary consumers. The first combined fridge-freezer came along in the US around 20 years later in 1939.
Refrigeration meant that, for the first time, families with no means of growing their own food or space to keep animals could experience a far more varied and nutritious diet.
Fresh fruit and vegetables became staples. People could taste exotic and previously unknown produce, imported from abroad using refrigeration on ships.
Houses no longer had to be built within easy reach of farms or other food producers.
Instead of buying and eating food the same day, shoppers were able to stock up, making savings by buying in bulk, and store it for long periods.
Milk could be kept for days, not hours.
Primitive methods of keeping food cool — some of them barely changed from Roman times but still used in 1930s Britain — were finally consigned to history.
