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Frozen Food

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.”

That memory served him well when he became an assistant to the president of the U.S. Fisheries Association in 1920. The fishing industry had always struggled to better preserve its highly perishable products and keep prices steady despite fluctuations in the catch. Birdseye’s stay in Labrador had impressed on him both the advantages of freezing and the disadvantages of existing methods. In 1923 he began working full-time in a New Jersey icehouse on his frozen-food process. The following year he moved to Gloucester, Massachusetts, and set up a small firm called General Seafoods Corporation, which was later renamed the General Foods Company.

Birdseye’s freezing processes—he developed two—did not require new scientific knowledge or a great conceptual breakthrough. Both centered on the key innovation of packing food before freezing it. After being placed within a convenient rectangular form, a food product could have direct contact with the freezing surface. Insulated from the processing equipment, the food never touched it or any chemicals, eliminating sanitary problems.

In Birdseye’s first patent, “Method of Preserving Piscatorial Products,” the package was held between two metal belts, which were chilled by a very cold (-40° to -45°F) calcium chloride solution. His second method, which came to be the more widely employed, was even simpler. Packaged food was held under pressure between two hollow metal plates chilled to -25°F by the vaporization of ammonia. A two-inch-thick package of meat could be frozen to 0°F in about 90 minutes this way; fruits and vegetables required half an hour more.

While conceptually simple, the process required many auxiliary devices and procedures. Eventually no fewer than 168 patents covered the machines that sliced the food, filled and sealed the boxes, and created the special paper and packages that could stand up to the extreme conditions. A boost in quality came in 1930, when H. C. Diehl and C. A. Magoon of the U.S. Bureau of Plant Industry found that successful quick-freezing of vegetables required the prior application of heat. Destructive enzymatic action known as autolysis, which leads to unpleasant flavors, occurs even at subfreezing temperatures, but it can be forestalled if vegetables are briefly scalded before freezing.

Completed in 1924, Birdseye’s first freezer weighed nearly 20 tons. Soon 10-shelf portable freezers of one-quarter that weight were in use, enabling the quick-freezing of produce close to the point of harvest.

The technological foundation of the frozen-food industry had been laid in the 1930s and 1940s, but commercial success lagged: in 1945 Americans still bought less than two pounds of frozen food on average. The frozen-food industry exploded during the consumer boom of the 1950s, during which many people bought refrigerators and freezers. Major changes in work and domestic life began to change the conventional understanding of what constituted a proper meal and who should prepare it. More women began working outside the home, and commuting distances lengthened. Families no longer necessarily took their meals together.