How did people keep food cold in olden times?

Violet, 5, wants to know: what was life like before refrigerators? And Ellinor, 6, asks: how did they make ice in the old times? In this episode, we learn about the history of ice harvesting and the industry that built up around it, where ice cut from lakes in New England was shipped to as far away as India and the Caribbean.

And in other places... Ancient physics at work to make Ice in the desert where it never freezes not even in winter...

The Persian ice house

Everyone can appreciate the cooling effect of a cold, iced drink on a hot summer day. How did people in hot climates even survive before there was electricity and freezers? Surely it would have been impossible to have ice at least? Well, as a matter of fact it wasn’t, and people in the deserts of Iran were enjoying frozen drinks well before electricity, thanks to the Persian ice house. Although ice houses that store natural ice and snow harvested during the winter have existed in many countries, the Persian ice house is unique because of the way the ice was made in the desert at temperatures above freezing.

Even though winter nights can be very cold in the deserts of Iran, temperatures rarely drop below freezing. But ice could be made even at temperatures just above freezing, thanks to a phenomenon known as night sky radiation or radiative cooling.

Outside the ice house there were shallow pools or channels, and these were shaded with walls during the day so that they remained as cool as possible. These pools were then filled with water on clear winter nights, and how much water was poured in the pool varied depending on how cold it was. The water came from the qanat system of underground aqueducts that brought water into the desert cities.

https://fieldstudyoftheworld.com/persian-ice-house-how-make-ice-desert/

And ancient Zeer Pot evaporative Refrigerators

A clay pot is filled with damp sand, which contains another smaller pot, in which food is placed. The evaporation of the water that moistens the sand contained in the cavity between the two pots produces cooling, bringing the heat of the inner vessel outwards.
Then it is covered with a wet cloth; the sand is kept humid by pouring water.
Evaporative cooling= temperature + humidity + air speed.
By maintaining a constant flow of fresh air, the temperature of the internal pot can reach up to 4.4 °C, a temperature at which mesophilic bacteria harmful to food significantly slow their growth.

This technique was already used in Ancient Egypt around 2500 B.C. In the 90s, in the rural areas of northern Nigeria, Mohamed Bah Abba (1964-2010), university professor, resumed this technology and spread it. The system has been successfully adopted in sub-Saharan Africa, has allowed to reduce diseases related to poor food storage and has granted several economic benefits to populations.

https://www.tecnosoft.eu/en/news/ZEER_desert_refrigerator/

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