Frozen Food

The history of frozen food goes back to middle 1800’s. As early as 1861 fish was frozen with ice and salt and stored for 8 to 10 months. The first successful ocean shipment of frozen meat was on the French ship Paraguay in 1878 when it sailed from Buenos Aires to France. In 1880 the S.S.Strathleven transported a load of frozen meat from Australia to England. In North America during a scientific expedition to Labrador in the years 1912–1915 expedition member Clarence Bird- seye noticed that fish frozen at subzero temperatures maintained their quality for long periods of time.

The modern era for frozen foods began with the discovery of quick freezing. By freezing the product within several hours (or several minutes in the case of food in small particles) rather than days, the build-up of microscopic ice crystals in the interior of the product is avoided. The frozen food market in the U.S. has grown from 180,000 kg (400,000 lb) in 1942 to 6 billion kg (13 billion lb) in 1995.

Popular methods of freezing food include air-blast freezing (where lowtemperature air passes at high velocity over food packages), contact freezing (packed or unpacked food is placed between refrigerated plates), immersion freezing (food is immersed in low-temperature brine), belt freezers which force lowtemperature air at high velocity from underneath the belt, spiral freezers where the product is conveyed on a conveyer belt within a low-temperature
chamber, and cryogenic freezing using liquid carbon dioxide or nitrogen.

In the distribution chain, frozen foods must be stored, perhaps first in large refrigerated warehouses, then later in small quantities near the grocery market. Storage temperatures for frozen foods are typically between -20°C (-5°F) and -23°C (-10°F), although some products such as fish and ice cream are usually stored at lower temperatures. Warehouses storing fish often maintain temperatures as low as -30°C (-22°F). A food like ice cream behaves similarly to brine or antifreeze. The water begins to freeze at a certain temperature which concentrates the remainder and lowers its freezing temperature. The range of temperatures through which ice cream passes as it freezes starts at about -2°C (28° F) and ultimately reaches -30°C (-22°F). Ice cream is packaged at about -5°C (23°F) at which temperature it is stiff, but will still flow. Then it moves to a hardening room kept at -30°C (-22°F) for complete freezing.

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