Throughout the history of mankind science has searched into the realms of the unknown.
Along with it bringing new discoveries, allowing for our lives to become healthier, more
efficient, safer, and at the same time, possibly more dangerous. Among the forces driving
scientists into these many experiments, is the desire to preserve the one fuel that keeps
our lives going; FOOD.
As early as the beginning of the 19th century, major breakthroughs in food preservation
had begun. Soldiers and seamen, fighting in Napoleons army were living off of
salt-preserved meats. These poorly cured foods provided minimal nutritional value, and
frequent outbreaks of scurvy were developing. It was Napoleon who began the search for a
better mechanism of food preservation, and it was he who offered 12,000-franc pieces to
the person who devised a safe and dependable food-preservation process.
The winner was a French chemist named Nicolas Appert. He observed that food heated in
sealed containers was preserved as long as the container remained unopened or the seal
did not leak. This became the turning point in food preservation history. Fifty years
following the discovery by Nicolas Appert, another breakthrough had developed. Another
Frenchman, named Louis Pasteur, noted the relationship between microorganisms and food
spoilage. This breakthrough increased the dependability of the food canning process. As
the years passed new techniques assuring food preservation would come and go, opening
new
doors to further research.
FOOD PROCESSING
Farmers grow fruits and vegetables and fatten livestock. The fruits and vegetables are
harvested, and the livestock is slaughtered for food. What happens between the time food
leaves the farm and the time it is eaten at the table? Like all living things, the plants
and animals that become food contain tiny organisms called microorganisms. Living,
healthy plants and animals automatically control most of these microorganisms. But when
the plants and animals are killed, the organisms yeast, mold, and bacteria begin to
multiply, causing the food to lose flavor and change in color and texture. Just as
important, food loses the nutrients that are necessary to build and replenish human
bodies. All these changes in the food are what people refer to as food spoilage. To keep
the food from spoiling, usually in only a few days, it is preserved. Many kinds of agents
are potentially destructive to the healthful characteristics of fresh foods.
Microorganisms, such as bacteria and fungi, rapidly spoil food. Enzymes which are present
in all raw food, promote degradation and chemical changes affecting especially texture
and flavor. Atmospheric oxygen may react with food constituents, causing rancidity or
color changes. Equally as harmful are infestations by insects and rodents, which account
for tremendous losses in food stocks. There is no single method of food preservation that
provides protection against all hazards for an unlimited period of time. Canned food
stored in Antarctica near the South Pole, for example, remained edible after 50 years of
storage, but such long-term preservation cannot be duplicated in the hot climate of the
Tropics.
Raw fruits and vegetables and uncooked meat are preserved by cold storage or
refrigeration. The cold temperature inside the cold-storage compartment or refrigerator
slows down the microorganisms and delays deterioration. But cold storage and
refrigeration will preserve raw foods for a few weeks at most. If foods are to be
preserved for longer periods, they must undergo special treatments such as freezing or
heating. The science of preserving foods for more than a few days is called food
processing.
Human beings have always taken some measures to preserve food. Ancient people learned to
leave meat and fruits and vegetables in the sun and wind to remove moisture. Since
microorganisms need water to grow, drying the food slows the rate at which it spoils.
Today food processors provide a diet richer and more varied than ever before by using six
major methods. They are canning, drying or dehydration, freezing, freeze-drying,
fermentation or pickling, and irradiation.
Canning
The process of canning is sometimes called sterilization because the heat treatment of
the food eliminates all microorganisms that can spoil the food and those that are harmful
to humans, including directly pathogenic bacteria and those that produce lethal toxins.
Most commercial canning operations are based on the principle that bacteria destruction
increases tenfold for each 10? C increase in temperature. Food exposed to high
temperatures for only minutes or seconds retains more of its natural flavor. In the Flash
18 process, a continuous system, the food is flash-sterilized in a pressurized chamber to
prevent the superheated food from boiling while it is placed in containers. Further
sterilizing is not required.
Freezing
Although prehistoric humans stored meat in ice caves, the food-freezing industry is more
recent in origin than the canning industry. The freezing process was used commercially
for the first time in 1842, but large-scale food preservation by freezing began in the
late 19th century with the advent of mechanical refrigeration.
Freezing preserves food by preventing microorganisms from multiplying. Because the
process does not kill all types of bacteria, however, those that survive reanimate in
thawing food and often grow more rapidly than before freezing. Enzymes in the frozen
state remain active, although at a reduced rate. Vegetables are blanched or heated in
preparation for freezing to ensure enzyme inactivity and thus to avoid degradation of
flavor. Blanching has also been proposed for fish, in order to kill cold-adapted bacteria
on their outer surface. In the freezing of meats various methods are used depending on
the type of meat and the cut. Pork is frozen soon after butchering, but beef is hung in a
cooler for several days to tenderize the meat before freezing.
Frozen foods have the advantage of resembling the fresh product more closely than the
same food preserved by other techniques. Frozen foods also undergo some changes, however.
Freezing causes the water in food to expand and tends to disrupt the cell structure by
forming ice crystals. In quick-freezing the ice crystals are smaller, producing less cell
damage than in the slowly frozen product. The quality of the product, however, may depend
more on the rapidity with which the food is prepared and stored in the freezer than on
the rate at which it is frozen. Some solid foods that are frozen slowly, such as fish,
may, upon thawing, show a loss of liquid called drip; some liquid foods that are frozen
slowly, such as egg yolk, may become coagulated. Because of the high cost of
refrigeration, frozen food is comparatively expensive to produce and distribute. High
quality is a required feature of frozen food to justify the added cost in the market.This
method of preservation is the one most widely used for a great variety of foods.
Drying and Dehydration
Although both these terms are applied to the removal of water from food, to the food
technologist drying refers to drying by natural means, such as spreading fruit on racks
in the sun, and dehydration designates drying by artificial means, such as a blast of hot
air. In freeze-drying a high vacuum is maintained in a special cabinet containing frozen
food until most of the moisture has sublimed. Removal of water offers excellent
protection against the most common causes of food spoilage. Microorganisms cannot grow in
a water-free environment, enzyme activity is absent, and most chemical reactions are
greatly retarded. This last characteristic makes dehydration preferable to canning if the
product is to be stored at a high temperature. In order to achieve such protection,
practically all the water must be removed. The food then must be packaged in a
moisture-proof container to prevent it from absorbing water from the air.
Vegetables, fruits, meat, fish, and some other foods, the moisture content of which
averages as high as 80 percent, may be dried to one-fifth of the original weight and
about one-half of the original volume. The disadvantages of this method of preservation
include the time and labor involved in rehydrating the food before eating. Further
because it absorbs only about two-thirds of its original water content, the dried product
tends to have a texture that is tough and chewy.
Drying was used by prehistoric humans to preserve many foods. Large quantities of fruits
such as figs have been dried from ancient times to the present day. In the case of meat
and fish, other preservation 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 19th century until the
beginning of the 20th 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 1980s, 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.
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