were living off of salt-preserved meats. These poorly cured foods provided
minimal nutritional value, and frequent outbreaks of scurvy were developing. It
and it was he who offered 12,000-franc pieces to the person who devised a safe
and dependable food-preservation process.
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
another breakthrough had developed. Another Frenchman, named Louis Pasteur,
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.
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
automatically control most of these microorganisms. But when the plants and
animals are killed, the organisms yeast, mold, and bacteria begin to multiply,
important, food loses the nutrients that are necessary to build and replenish
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.
preservation that provides protection against all hazards for an unlimited
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
remove moisture. Since microorganisms need water to grow, drying the food slows
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.
Although prehistoric humans stored meat in ice caves, the food-freezing
preservation by freezing began in the late 19th century with the advent of
Freezing preserves food by preventing microorganisms from multiplying.
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.
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
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
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
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
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,
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.
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
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.
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.
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
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.
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.
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
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
dehydrated foods. Calcium propionate may be added to baked goods to inhibit mold.
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
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.
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
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,
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
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.