FOOD PROCESSING METHODS

Press, Volume XCI, Issue 27634, 15 April 1955, Page 10

FOOD PROCESSING METHODS

Freezing Friiit After Dehydration

EXPERIMENTS OF U.S. SCIENTISTS

[U.S. Information Service] WASHINGTON.

United States’ scientists have developed a new food preservation process called “dehydrofreezing.” Apples, apricots, peas and pimientos are now being commercially preserved by this process. Other fruits and vegetables—Royal Anne cherries, freestone peaches, carrots, boysenberries and diced potatoes—have been tested, and will likely be added to the list of commerical products as the new industry expands.

The process was developed by the United States Department of Agriculture (USDA) at its Western Regional Research Laboratory in Albany, California. It provides a means of adequate preservation and. because of the great decrease in weight resulting from partial dehydration, for economical transportation from producing countries to other free nations. The “dehydrofreezing” process not only saves space and weight, but also retains the flavour and texture of fresh fruits and vegetables. Ordinary freezing tends to rupture, cellular structure and many frozeji fruits and vegetables break down somewhat when thawed for consumption. Cells that have been partially dehydrated, however, are not ruptured so easily by the freezing process. “Dehydrofrozen” foods retain approximately half their original weight and volume. They are reconstituted for use in the home by soaking them in water. Essentially, the process consists of: (1) Conventional preparation of the commodity as for regular canning oi' freezing. (2) Inactivation of enzymes, when necesary, to prevent browning. (3) Rapid drying to reduce weight and volume by approximately one-half. (4) Packaging and freezing. <5) Storage or transportation at 0 degrees Fahrenheit (minus 18 degrees Centigrade). Various types of drying equipment can be used, depending largely on the product. For instance, commercial prune-drying equipment has proved suitable for halved apricots, which take three to four hours for dehydration. Apple slices and pimientos can be dried in one hour or less. A continuous rotary drier has been devised by the department to suit the needs of the new process. This drier delivers air through the food by four separate ducts, eacq with a blower and steam coils. The tendency of foods to stick to the drum of the new machine has been partially overcome by a wiremesh liner that reduces the area of flat metal surface. Longitudinal wood strips around the inside of the drum assure 0 mixing rather than a sliding action. A slow rotating speed of four revolutions a minute avoids abrasion. Pies made from “dehydrofrozen” .apples are delicious—as good as any made from fresh fruit. In general, apple varieties that* are good for ordinary canning or freezing can also be used for “dehydrofreezing?’ r The flavour of, .apricot pies made from-“dehydrofrozen” fruit was found better in baking tests than that of pies made from frozen, dried or canned apricots prepared from the same lot of fruity Preserves prepared from “dehydrofrozen” apricots did not disintegrate during cooking. “Dehydrofrozen” pimientos have been found superior for use in soups, cheese and meat products. They hold

flavour unusually well, and their reduced moisture offers advantage in food manufacturing. After a year of storage at minus 10 degrees Fahrenheit, peas were found to be as good as ordinary frozen peas. Colour, flavour and texture were excellent. Estimates based on the experimental studies indicate that the processing costs of “dehydrofreezing” are a little higher than in quick freezing. Lower packaging, freezing, storage and distribution costs, however, are expected to result in an over-all saving.