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In the days when humans were hunter-gatherers, subsistence consumption was the only way humans knew for gathering food. There was no technology to store anything for long periods of time, so people were forced to hunt or collect only what they could eat immediately. With the advent of civilizations, the concentration of so many people created dedicated farming classes that could support people who spent their excess leisure time thinking of ways to solve problems such as this. The solution to this problem would eventually become our modern refrigeration systems.

Early refrigeration systems were simple pits lined with ice and snow, then covered with straw for insulation. Many cultures had come up with ingenious ways of combating food spoilage, but the most impressive solution to this problem was the one designed by the ancient Persians in about 500 BCE. This civilization build large domed structures called “yahkchals” which kept ice to a temperature equivalent to that of modern refrigerators. This is a clear case of necessity being the mother of invention, as the Persians required large amounts of ice to preserve food in the deserts that they lived in and around. These yahkchals were marvels of engineering, yet surprisingly simple. They achieved what they did simply by creating these buildings with thick walls made of a resilient, water-tight mortar known as sarooj. This material was made of sand, clay, animal hair, egg, and other substances in specific proportions, and it yielded a very thick material that could be built into an effective refrigeration system due to sarooj’s resistance to heat transfer. While food preservation was a necessity, the yahkchals were also used to preserve luxury foods for the Persian royalty because they were often the richest people who owned the largest and most numerous refrigeration systems.

Throughout the European Industrial Revolution, modern refrigeration systems began to be constructed that employed gas compression in order to preserve food for long distances. This brought forth a qualitative shift in shipping that opened up an entire industry when people realized food could be moved from any part of the world to another. This movement began in New Zealand when in 1881 a large merchant vessel named the Dunedin was fitted with a large cold storage unit to transport frozen meat to Great Britain. Despite the tremendous distance, this early foothold in what would quickly become a massive industry ensured New Zealand would dominate the meat shipping business in England for a hundred years. This method would not have worked with regular ice storage because merchant ships cannot deliver the same stable conditions as a Persian yahkchal. Gas compression became the wave of the future.

Today nearly all modern refrigerators employ gas compression technology. Throughout the past hundred years various innovative steps have been taken in improving the technology of refrigeration systems that generally caused quantitative leaps by allowing new transportation methods to be refrigerated, such as trucks and planes. The final quantitative leap yielded safer chemicals that allowed for commercial refrigerators to exist in smaller spaces such as households across the united states.



Source by Dan S Thaler