Refrigeration

The term refrigeration refers to any process by which heat is removed from an enclosed space or from a specific substance for the purpose of creating a cooled environment or lowering the temperature of the substance in question. Most often, refrigeration is used to facilitate the storage of various foodstuffs at low temperatures to prevent, or at least slow, the decomposition and spoilage caused by bacteria, yeast, and mold. In many developed nations, refrigeration is also used in air-conditioning systems to create the cool air needed to make indoor environmental temperature control possible.

Although primitive forms of refrigeration have been in use since antiquity, modern mechanical refrigeration methods only began to emerge in the latter half of the nineteenth century. The most revolutionary of these was the electric household refrigerator, which debuted in 1914 and could be found in virtually every American home by the 1950s. Refrigeration methods and technologies continue to evolve, with everything from magnetic refrigeration to biogel refrigeration being studied for possible future use.

Early Methods of Refrigeration

The use of rudimentary forms of refrigeration can be traced back to the ancient world. Even before the first millennium, the early Chinese began harvesting ice for refrigeration purposes. Later, affluent Greeks and Romans built ice pits in their homes that were insulated with wood and straw and filled with ice transported from nearby mountains. Ancient Egyptians made ice by taking advantage of a phenomenon known as evaporative cooling, which occurs when the rapid evaporation of water draws heat away from the water's immediate surroundings and thus allows for freezing. Many Egyptians simply placed an earthen jar filled with water on top of their roofs in the evening and awoke the next morning to ice produced by the cool night air.

By the seventeenth century, new approaches to refrigeration were being developed and adopted in Europe. Most notably, resourceful thinkers discovered that dissolving saltpeter in water yielded a solution that was capable of producing temperatures low enough to make ice. By rotating long-necked bottles in this solution, it was possible to make a variety of cooled and even iced drinks—a trend that became quite popular in France and throughout much of Southern Europe.

Refrigeration and the Industrial Revolution

As the modern world became more industrialized in the nineteenth century and the global population grew and spread, food preservation evolved into an increasingly pressing concern. Although traditional preservation methods like salting, drying, and smoking were still widely used, the growing distance between consumers and food sources made more reliable methods that could help preserve a wider variety of foods a greater necessity. This necessity eventually led to the rise of commercial ice shipping as a major industry, particularly in the United States. At the helm of this industry was "Ice King" Frederic Tudor and Nathaniel Wyeth, a pair of entrepreneurs who specialized in shipping ice to tropical climates and developed cutting methods, handling techniques, and insulating materials that drastically reduced melting losses. By the turn of the twentieth century, the success of the ice industry led to the emergence of the icebox as a common fixture in American homes. Often made of wood and lined with tin or zinc, iceboxes were cooled by large blocks of ice and provided a refrigerated environment in which perishable foodstuffs could be easily stored and preserved.

The Electric Refrigerator

While iceboxes were a practical solution for most consumers, other forms of refrigeration were also being developed. As early as the mid-eighteenth century, scientists began working to make artificial refrigeration a realistic possibility. The first successful attempt at producing artificial refrigeration was made by Scottish physician William Cullen, who accomplished this feat by boiling ethyl ether into a partial vacuum in 1748. Later, in 1805, American inventor Oliver Evans designed the first artificial refrigeration machine to use vapor rather than liquid. In the years that followed, vapor-compression machines like the one developed by Evans became the industry standard.

Although artificial refrigeration quickly came to enjoy widespread use in commercial applications, it did not immediately find a niche in the consumer market. This was because early vapor-compression refrigeration units used ammonia, an unpleasant and potentially toxic liquid, as a coolant. When Freon, an odorless and much safer synthetic refrigerant, was developed in the 1920s, however, consumer refrigeration became a more realistic possibility.

With the creation of Freon, the electric refrigerator became wildly popular. By the 1930s, electric refrigerators began replacing iceboxes in many American homes, in part because of funds made available to consumers through government loans. These reliable electric refrigerators enabled homeowners to preserve virtually every type of perishable food and even reduced waste by making leftovers a staple of the American diet. By mid-century, electric refrigerators could be found in virtually every home nationwide.

The Future of Refrigeration

Through the second half of the twentieth century and into the twenty-first century, home refrigerators continued to evolve. In the 2010s, refrigerators entered the digital age with the development of the first smart refrigerator. Connected to the Internet, these refrigerators were designed to help consumers keep track of their food supply and even order more groceries when necessary.

Along with improvements to standard vapor-compression refrigerators, researchers also began to explore other technological approaches to refrigeration. One example of a new potential method of refrigeration is the magnetic refrigerator, which uses magnets to create a magnetic field that agitates particles and thereby cools a water-based fluid that replaces traditional chemical refrigerants. Another example is the proposed Bio Robot Refrigerator, which will theoretically feature a cooled biopolymer gel into which foods can be placed and kept fresh.

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