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... methods, such as smoking or salting, which yielded a palatable product, were generally preferred. Commercial dehydration of vegetables was initiated in the United States during the American Civil War but, as a result of the poor quality of the product, the industry declined sharply after the war. This cycle was repeated with subsequent wars, but after World War II the dehydration industry thrived. This industry is confined largely to the production of a few dried foods, however, such as milk, soup, eggs, yeast, and powdered coffee, which are particularly suited to the dehydration method. Present-day dehydration techniques include the application of a stream of warm air to vegetables.
Protein foods such as meat are of good quality only if freeze-dried. Liquid food is dehydrated usually by spraying it as fine droplets into a chamber of hot air, or occasionally by pouring it over a drum internally heated by steam. Freeze-drying A processing method that uses a combination of freezing and dehydration is called freeze-drying. Foods that already have been frozen are placed in a vacuum-tight enclosure and dehydrated under vacuum conditions with careful application of heat. Normally ice melts and becomes water when heat is applied. If more heat is applied, it turns to steam.
But in freeze-drying, the ice turns directly to vapor, and there is little chance that microorganisms will grow. Freeze-dried foods, like those that are dehydrated, are light and require little space for storage and transportation. They do not need to be refrigerated, but they must be reconstituted with water before they are ready to consume. Irradiation As early as 1895, a major breakthrough in the world of science had arisen; the discovery of the X-ray by German physicist Wilhelm von Roetengen. This technological advancement, along with the soon to be discovered concept of radioactivity by French physicist Antoine Henri Becquerel, became the focus of attention for many scientifically based studies. Of most importance, to the field of food preservation, these two discoveries began the now controversial process of food irradiation.
Food irradiation employs an energy form termed ionizing radiation. In short, this process exposes food particles to alpha, beta and / or gamma rays. The rays cause whatever material they strike to produce electrically charged particles called ions. Ionizing radiation provides many attributes to treating foods. It has the ability to penetrate deeply into a food interacting with its atoms and molecules, and causing some chemical and biological effects that could possibly decrease its rate of decay. It also has the ability to sanitize foods by destroying contaminants such as bacteria, yeasts, molds, parasites and insects.
Irradiation delays ripening of fruits and vegetables; inhibits sprouting in bulbs and tubers; disinfests grain, cereal products, fresh and dried fruits, and vegetables of insects; and destroys bacteria in fresh meats. The irradiation of fresh fruits and vegetables, herbs and spices, and pork was approved in 1986. In 1990 the FDA approved irradiation of poultry to control salmonella and other disease-causing microorganisms. Irradiated foods were used by U. S. astronauts and by Soviet cosmonauts.
Public concern over the safety of irradiation, however, has limited its full-scale use. It is still off to a slow start, with only one food irradiation plant open in Mulberry, Florida, but it is seemingly catching the eyes of the producers and the consumers throughout the world. Miscellaneous Methods Other methods or a combination of methods may be used to preserve foods. Salting of fish and pork has long been practiced, using either dry salt or brine. Salt enters the tissue and, in effect binds the water, thus inhibiting the bacteria that cause spoilage.
Another widely used method is smoking, which frequently is applied to preserve fish, ham, and sausage. The smoke is obtained by burning hickory or a similar wood under low draft. In this case some preservative action is provided by such chemicals in the smoke as formaldehyde and creosote, and by the dehydration that occurs in the smokehouse. Smoking usually is intended to flavor the product as well as to preserve it. Sugar, a major ingredient of jams and jellies, is another preservative agent.
For effective preservation the total sugar content should make up at least 65 percent of the weight of the final product. Sugar, which acts in much the same way as salt, inhibits bacterial growth after the product has been heated. Because of its high acidity, vinegar (acetic acid) acts as a preservative. Fermentation caused by certain bacteria, which produce lactic acid, is the basis of preservation in sauerkraut and fermented sausage. Sodium benzoate, restricted to concentrations of not more than 0. 1 percent, is used in fruit products to protect against yeasts and molds.
Sulfur dioxide, another chemical preservative permitted in most states, helps to retain the color of dehydrated foods. Calcium propionate may be added to baked goods to inhibit mold. Packaging The packaging of processed foods is just as important as the process itself. If foods are not packaged in containers that protect them from air and moisture, they are subject to spoilage. Packaging materials must therefore be strong enough to withstand the heat and cold of processing and the wear and tear of handling and transportation. From the time the canning process was developed in the early 19 th century until the beginning of the 20 th century, cans and glass containers were the only packages used.
The first cans were crude containers having a hole in the top through which the food was inserted. The holes were then sealed with hot metal. All cans were made by hand from sheets of metal cut to specific sizes. In about 1900 the sanitary can was invented. In this process, machines form cans with airtight seams. A processor buys cans with one end open and seals them after filling.
Some cans are made of steel coated with tin and are often glazed on the inside to prevent discoloration. Some are made of aluminum. Frozen foods are packaged in containers made of layers of fiberboard and plastic or of strong plastic called polyethylene. Freeze-dried and dehydrated foods are packed in glass, fiberboard, or cans. Research The research activities of processed food scientists are numerous and varied. New packaging materials, the nutritional content of processed foods, new processing techniques, more efficient use of energy and water, the habits and desires of today's consumer, more efficient equipment, and transportation and warehousing innovations are some of the subjects being studied.
The challenge of the food researcher is to discover better and more efficient ways to process, transport, and store food. Processed foods have changed the world. In developed countries they are part of almost everyone's diet. The United States, Canada, France, Germany, Italy, Portugal, Spain, and the United Kingdom all produce large quantities of processed foods, which they sell domestically and abroad. In the United States in the early 1980 s, annual production of fruit was 1. 8 billion kilograms canned, 1. 4 billion kilograms frozen, and 1. 1 billion kilograms in fruit juice; production of vegetables was 1. 4 billion kilograms canned and 3. 2 billion kilograms frozen. From the modest canning industries in 1813 to the sophisticated food processing plants of today, food processors have provided the world with more healthful diets, food combinations never before possible, and a convenience unimagined 200 years ago.
We as consumers can only imagine what further achievements will be made in the field of food preservation. But one thing is for certain; it is all for the general good of mankind... to reduce starvation levels globally and insure the availability of nutritive foods to all. It is through this way that man survives... and fits in Darwin's hypothesis of the survival of the fittest. For it is only the fit who will prevail in the end.
References Fellows, P. J. Food Processing Technology Ellis Horwood Ltd: (1990) Grolier Interactive Encyclopaedia Harris Robert S. and Von Lesecke, Harry. Nutritional Evaluation of Food Processing Avi Publishing Co: (1973) Popular Science Encyclopaedia Grolier Incorporated: (1980)
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Research essay sample on Food Processing And Preservation
