History Of Refrigeration

Refrigeration applied both above and below the freezing point of foods has been used for thousands of years to preserve foods and to increase comfort. Historians estimate that caves were used for food storage about 100,000 yr ago (1).

Temperature inside the caves is naturally low as a result of the evaporization of water, which is often present.

An Egyptian frieze from 3000 b.c. shows a slave waving a fan in front of a clay pot. The cooling effect from vaporization of water was also utilized in this case. Egyptians also utilized terrestrial radiation toward space at night under a clear sky to produce ice.

Ice was used locally when available. Later it was harvested during wintertime and stored for the summer season. In 1100 b.c. a Chinese poem mentioned ice houses. Ice and snow were transported over great distances, eg, from the Apennines to Rome, and caravans were transporting ice and snow from Lebanon to the palaces of the Califs of Damascus, Baghdad, and the sultans in Cairo.

In many countries ice was believed to be a gift of the gods to humans. This was confirmed as late as during the mid-nineteenth century, when the American John Goorie in 1844 managed to produce ice with an air compressor but did not dare to publish the invention under his own name. Instead, under a pseudonym he wrote a scientific article describing an ice machine as a future possibility. The New York newspaper, The Globe, shortly after published an article titled "Some lunatic in Florida believes his machine can make ice equally good as the All Mighty."

Obviously hunters and gatherers living in a cold climate did use the natural freezing of their food products in order to preserve them over long periods of time.

Exactly when the temperature-decreasing effect—with the addition of certain salts to water—was discovered is not known. There is, however, reason to believe that the method was used in India in the fourth century a. d. During the fourteenth and fifteenth century a number of European scientists were working with salt solutions and managed to achieve temperatures as low as —15 to — 20°C. With those salt mixtures the stage between natural and artificial cooling was passed.

It was not until 1755, however, that the first apparatus for making ice was constructed by William Cullen. Vaporization of water at reduced pressure was utilized.

During the first half of the nineteenth century four events of fundamental importance for the refrigeration industry took place: (1) the systematic work on the liquefaction of gases, (2) the genesis of thermodynamics originated by Nicolas Carnot in 1824 on the invention of the refrigeration machine using compression of a liquefiable gas (often referred to as the Carnot engine), (3) Jacob Perkins's work in mechanical refrigeration in 1834, and (4) the air cycle machine (Goorie, 1844); the latter two inventions remained undeveloped for two decades.

The start of industrial freezing of food is often set at around 1880, even if the first industrial installations were made some 20 years earlier. During 1870-1880 frozen meat was transported from the southern hemisphere to Europe. Initially those endeavors were unsuccessful. In beef cargo from Buenos Aires to Rouen (port on Seine River) in France as much as 25% in weight was lost by sublimation and the quality was unacceptable. The breakthrough came in 1877 when a shipment of frozen meat was brought in from Buenos Aires to Marseilles on the steamer Paraguay (2). This shipment was followed by another one from South America to New York in 1879, and in 1880 the steamer Strathleven made the journey from Sydney and Melbourne to London.

As compared to the quality achieved today, much was to be wished for. The freezing was carried out very slowly and the storage temperatures were high compared to the

8. R. J. Bellows and C. J. King, "Freeze Drying of Aqueous Solutions: Maximum Allowable Operating Temperatures," Cryobi-ology 9, 559 (1972).

9. H. G. A. Unger, "Revolution in Freeze Drying," Food Processing Industry 51, 20 (April 1982).

Henry Schwartzberg University of Massachusetts Amherst, Massachusetts

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