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Frozen Food

Fall 2010 | Volume 25 |  Issue 3

Even as late as a century ago, the diet of most Americans depended largely on what vegetables and fruits were available at the moment. “Putting up foods”— such as the drying and smoking of meat and the canning of fruits and vegetables—was an integral and often exhausting aspect of domestic life. Toward the end of the 19th century commercial canners began offering a wider variety of foodstuffs but still couldn’t compete with fresh food in flavor or nutritional value.

A natural alternative was freezing food, but that only occurred in very cold climates. Simply packing food in ice would not chill it fast enough or keep it cold enough. Early commercial efforts included an 1861 patent for freezing whole fish by using pans filled with salt and ice.

An 1867 patent featured a technique of spraying a cold liquid onto food in a partially evacuated chamber. The ensuing rapid evaporation drew heat from the food quickly. These and similar methods were widely adopted by fish wholesalers; by the end of the century, ice-and-salt freezers were in use in virtually all the fishing ports of the Great Lakes, New England, and New York State, where ice cut from lakes and streams was plentiful.

While these methods somewhat evened out the seasonal fluctuations in the availability of certain foods, they still didn’t work fast enough. When foods are frozen slowly, as happens when ice or even an ice-and-salt mixture is used, they are irreversibly damaged. Some of the damage results from the extraction of water from colloids of individual cells, which leads to the collapse of their walls, the concentration of salts, and the precipitation of proteins. All this makes for mushy food. Even worse, slow freezing produces large ice crystals that rupture cell membranes and break up tissue. When the food is defrosted, liquid leaks out, further harming flavor and texture.

By the 20th century, researchers had determined that maximum crystal formation occurred between 31° and 25°F. Damage could be minimized if a product was brought below that temperature range as quickly as possible. A number of inventors tried their hands at quick-freezing processes, and none was more successful than Clarence Birdseye.

An Amherst College dropout, he had sought his fortune in Labrador as a fur trader in 1912. “That first winter,” Birdseye wrote, “I saw natives catching fish in fifty below zero weather, which froze stiff almost as soon as they were taken out of the water. Months later, when they were thawed out, some of these fish were still alive.”

We hope you enjoyed this essay.

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