One of the first products of the frozen-food industry, and still one of the most popular, is the ordinary green pea. Its journey from field to consumer illustrates the basic processes involved in the production of frozen food.
An advantage of freezing is that peas and other foods can be harvested and packed at their peak flavor, regardless of market demand at the time. Frozen-food companies employ field agents to keep close watch on crops, monitor their growth, and decide when they should be harvested. On occasion portable freezers are brought to the fields, but transportation improvements have made this less necessary, for the harvest can usually be brought to a freezing plant in less than six hours.
Peas are first beaten from their pods by a machine called a viner, either in the field or at a processing plant. Other kinds of vegetables require slicing, dicing, or chopping, but peas occur naturally in convenient size. Loose peas are treated with steam or near-boiling water to slow down enzymatic action. They are then put into the cartons in which they will be sold, wrapped with moisture-resistant paper, and moved to the freezer.
Commercial packers use two basic methods of freezing. One of them is the convection method, in which packaged food moves along a conveyor belt while cold air is blown over it at about ten miles per hour. This method is used for irregularly shaped objects, such as whole poultry, and when it is desirable to keep items loose, as with peas in bags. In some cases, to save space, the conveyor is a stacked helix that carries the packages along a spiral path.
The other method is Clarence Birdseye’s conduction process, with metal plates containing refrigerant. This technique is more energy-efficient and especially suitable for food packed in straight-sided boxes. The packages are loaded onto stacks of the plates and are slightly compressed while refrigerant runs through the plates. The temperature in each box is brought down to -25°F in a few minutes. Many kinds of refrigerant have been used, including brine, dichlorodifluoromethane (CCl 2 F 2 , also known as Freon-12), and various glycols. Now packers are switching to new refrigerants to reduce environmental damage, especially ozone depletion.
After the peas have been quick-frozen, the pressure on the plates is released and the individual boxes are packed in shipping cartons. They are then transported to a refrigerated warehouse by truck or, less often, by rail. Within a few days the frozen foods are trucked to a retail store, reposing at a temperature of 0° while awaiting the final destination, the stoves and microwave ovens of consumers.
—R.V.
