See Food preservation - Encyclopedia.com
Link to "Curing Food"
preserve with oil
Open a can of food without a can opener(rub can lid ridge on cement and then pry open with knife)
Early Americans could only get fresh fruits and
vegetables during the growing season. There were no refrigerated rail cars or trucks
to bring food from more temperate climates. For the rest of the year they had to rely
on food preservation techniques that were difficult and time-consuming.
Methods available for preserving food included drying, salting, sugaring,
pickling and cold storage. These methods had been developed through trial and
error, but no one knew exactly why they worked. Bacteria had not yet been
We now know that drying, salting and sugaring reduce the activity of water.
This inhibits the growth of bacteria and the activity of internal enzymes that
cause food spoilage. Acidification and salting inhibit the growth of many spoilage
bacteria, and the low temperatures in cold storage slow down their reproductive
The term food preservation refers to any one of a number of techniques used to prevent food from spoiling. It includes methods such as canning, pickling, drying and freeze-drying, irradiation, pasteurization , smoking, and the addition of chemical additives. Food preservation has become an increasingly important component of the food industry as fewer people eat foods produced on their own lands, and as consumers expect to be able to purchase and consume foods that are out of season.
The vast majority of instances of food spoilage can be attributed to one of two major causes: (1) the attack by pathogens (disease-causing microorganisms ) such as bacteria and molds, or (2) oxidation that causes the destruction of essential biochemical compounds and/or the destruction of plant and animal cells. The various methods that have been devised for preserving foods are all designed to reduce or eliminate one or the other (or both) of these causative agents.
For example, a simple and common method of preserving food is by heating it to some minimum temperature. This process prevents or retards spoilage because high temperatures kill or inactivate most kinds of pathogens. The addition of compounds known as BHA and BHT to foods also prevents spoilage in another different way. These compounds are known to act as antioxidants, preventing chemical reactions that cause the oxidation of food that results in its spoilage. Almost all techniques of preservation are designed to extend the life of food by acting in one of these two ways.
The search for methods of food preservation probably can be traced to the dawn of human civilization. People who lived through harsh winters found it necessary to find some means of insuring a food supply during seasons when no fresh fruits and vegetables were available. Evidence for the use of dehydration (drying) as a method of food preservation, for example, goes back at least 5,000 years. Among the most primitive forms of food preservation that are still in use today are such methods as smoking, drying, salting, freezing, and fermenting.
Early humans probably discovered by accident that certain foods exposed to smoke seem to last longer than those that are not. Meats, fish, fowl, and cheese were among such foods. It appears that compounds present in wood smoke have antimicrobial actions that prevent the growth of organisms that cause spoilage. Today, the process of smoking has become a sophisticated method of food preservation with both hot and cold forms in use. Hot smoking is used primarily with fresh or frozen foods, while cold smoking is used most often with salted products. The most advantageous conditions for each kind of smoking—air velocity, relative humidity, length of exposure, and salt content, for example—are now generally understood and applied during the smoking process. For example, electrostatic precipitators can be employed to attract smoke particles and improve the penetration of the particles into meat or fish. So many alternative forms of preservation are now available that smoking no longer holds the position of importance it once did with ancient peoples. More frequently, the process is used to add interesting and distinctive flavors to foods.
Because most disease-causing organisms require a moist environment in which to survive and multiply, drying is a natural technique for preventing spoilage. Indeed, the act of simply leaving foods out in the sun and wind to dry out is probably one of the earliest forms of food preservation. Evidence for the drying of meats, fish, fruits, and vegetables go back to the earliest recorded human history. At some point, humans also learned that the drying process could be hastened and improved by various mechanical techniques. For example, the Arabs learned early on that apricots could be preserved almost indefinitely by macerating them, boiling them, and then leaving them to dry on broad sheets. The product of this technique, quamaradeen, is still made by the same process in modern Muslim countries.
Today, a host of dehydrating techniques are known and used. The specific technique adopted depends on the properties of the food being preserved. For example, a traditional method for preserving rice is to allow it to dry naturally in the fields or on drying racks in barns for about two weeks. After this period of time, the native rice is threshed and then dried again by allowing it to sit on straw mats in the sun for about three days. Modern drying techniques make use of fans and heaters in controlled environments. Such methods avoid the uncertainties that arise from leaving crops in the field to dry under natural conditions. Controlled temperature air drying is especially popular for the preservation of grains such as maize, barley, and bulgur.
Vacuum drying is a form of preservation in which a food is placed in a large container from which air is removed. Water vapor pressure within the food is greater than that outside of it, and water evaporates more quickly from the food than in a normal atmosphere. Vacuum drying is biologically desirable since some enzymes that cause oxidation of foods become active during normal air drying. These enzymes do not appear to be as active under vacuum drying conditions, however. Two of the special advantages of vacuum drying are that the process is more efficient at removing water from a food product, and it takes place more quickly than air drying. In one study, for example, the drying time of a fish fillet was reduced from about 16 hours by air drying to six hours as a result of vacuum drying.
Coffee drinkers are familiar with the process of dehydration known as spray drying. In this process, a concentrated solution of coffee in water is sprayed though a disk with many small holes in it. The surface area of the original coffee grounds is increased many times, making dehydration of the dry product much more efficient. Freeze-drying is a method of preservation that makes use of the physical principle known as sublimation. Sublimation is the process by which a solid passes directly to the gaseous phase without first melting. Freeze-drying is a desirable way of preserving food because at low temperatures (commonly around 14°F to –13°F [–10°C to –25°C]) chemical reactions take place very slowly and pathogens have difficulty surviving. The food to be preserved by this method is first frozen and then placed into a vacuum chamber. Water in the food first freezes and then sublimes, leaving a moisture content in the final product of as low as 0.5%.
The precise mechanism by which salting preserves food is not entirely understood. It is known that salt binds with water molecules and thus acts as a dehydrating agent in foods. A high level of salinity may also impair the conditions under which pathogens can survive. In any case, the value of adding salt to foods for preservation has been well known for centuries. Sugar appears to have effects similar to those of salt in preventing spoilage of food. The use of either compound (and of certain other natural materials) is known as curing. A desirable side effect of using salt or sugar as a food preservative is, of course, the pleasant flavor each compound adds to the final product.
Curing can be accomplished in a variety of ways. Meats can be submerged in a salt solution known as brine, for example, or the salt can be rubbed on the meat by hand. The injection of salt solutions into meats has also become popular. Food scientists have now learned that a number of factors relating to the food product and to the preservative conditions affect the efficiency of curing. Some of the food factors include the type of food being preserved, the fat content, and the size of treated pieces. Preservative factors include brine temperature and concentration, and the presence of impurities.
Curing is used with certain fruits and vegetables, such as cabbage (in the making of sauerkraut), cucumbers (in the making of pickles), and olives. It is probably most popular, however, in the preservation of meats and fish. Honey-cured hams, bacon, and corned beef ("corn" is a term for a form of salt crystals) are common examples.
Freezing is an effective form of food preservation because the pathogens that cause food spoilage are killed or do not grow very rapidly at reduced temperatures. The process is less effective in food preservation than are thermal techniques such as boiling because pathogens are more likely to be able to survive cold temperatures than hot temperatures. In fact, one of the problems surrounding the use of freezing as a method of food preservation is the danger that pathogens deactivated (but not killed) by the process will once again become active when the frozen food thaws.
A number of factors are involved in the selection of the best approach to the freezing of foods, including the temperature to be used, the rate at which freezing is to take place, and the actual method used to freeze the food. Because of differences in cellular composition, foods actually begin to freeze at different temperatures ranging from about 31°F (–0.6°C) for some kinds of fish to 19°F (–7°C) for some kinds of fruits.
The rate at which food is frozen is also a factor, primarily because of aesthetic reasons. The more slowly food is frozen, the larger the ice crystals that are formed. Large ice crystals have the tendency to cause rupture of cells and the destruction of texture in meats, fish, vegetables, and fruits. In order to deal with this problem, the technique of quick-freezing has been developed. In quick-freezing, a food is cooled to or below its freezing point as quickly as possible. The product thus obtained, when thawed, tends to have a firm, more natural texture than is the case with most slow-frozen foods.
About a half dozen methods for the freezing of foods have been developed. One, described as the plate, or contact, freezing technique, was invented by the American inventor Charles Birdseye in 1929. In this method, food to be frozen is placed on a refrigerated plate and cooled to a temperature less than its freezing point. Alternatively, the food may be placed between two parallel refrigerated plates and frozen. Another technique for freezing foods is by immersion in very cold liquids. At one time, sodium chloride brine solutions were widely used for this purpose. A 10% brine solution, for example, has a freezing point of about 21°F (–6°C), well within the desired freezing range for many foods. More recently, liquid nitrogen has been used for immersion freezing. The temperature of liquid nitrogen is about –320°F (–195.5°C), so that foods immersed in this substance freeze very quickly.
As with most methods of food preservation, freezing works better with some foods than with others. Fish, meat, poultry, and citrus fruit juices (such as frozen orange juice concentrate) are among the foods most commonly preserved by this method.
Fermentation is a naturally occurring chemical reaction by which a natural food is converted into another form by pathogens. It is a process in which food spoils, but results in the formation of an edible product. Perhaps the best example of such a food is cheese. Fresh milk does not remain in edible condition for a very long period of time. Its pH is such that harmful pathogens begin to grow in it very rapidly. Early humans discovered, however, that the spoilage of milk can be controlled in such a way as to produce a new product, cheese.
Bread is another food product made by the process of fermentation. Flour, water, sugar, milk, and other raw materials are mixed together with yeasts and then baked. The addition of yeasts brings about the fermentation of sugars present in the mixture, resulting in the formation of a product that will remain edible much longer than will the original raw materials used in the bread-making process.
Heating food is an effective way of preserving it because the great majority of harmful pathogens are killed at temperatures close to the boiling point of water. In this respect, heating foods is a form of food preservation comparable to that of freezing but much superior to it in its effectiveness. A preliminary step in many other forms of food preservation, especially forms that make use of packaging, is to heat the foods to temperatures sufficiently high to destroy pathogens.
In many cases, foods are actually cooked prior to their being packaged and stored. In other cases, cooking is neither appropriate nor necessary. The most familiar example of the latter situation is pasteurization. During the 1860s, the French bacteriologist Louis Pasteur discovered that pathogens in foods could be destroyed by heating those foods to a certain minimum temperature. The process was particularly appealing for the preservation of milk since preserving milk by boiling is not a practical approach. Conventional methods of pasteurization called for the heating of milk to a temperature between 145 and 149°F (63 and 65°C) for a period of about 30 minutes, and then cooling it to room temperature. In a more recent revision of that process, milk can also be "flash-pasteurized" by raising its temperature to about 160°F (71°C) for a minimum of 15 seconds, with equally successful results. A process known as ultra-high-pasteurization uses even higher temperatures, of the order of 194–266°F (90–130°C), for periods of a second or more.
One of the most common methods for preserving foods today is to enclose them in a sterile container. The term "canning" refers to this method although the specific container can be glass, plastic, or some other material as well as a metal can, from which the procedure originally obtained its name. The basic principle behind canning is that a food is sterilized, usually by heating, and then placed within an air-tight container. In the absence of air, no new pathogens can gain access to the sterilized food. In most canning operations, the food to be packaged is first prepared in some way—cleaned, peeled, sliced, chopped, or treated in some other way—and then placed directly into the container. The container is then placed in hot water or some other environment where its temperature is raised above the boiling point of water for some period of time. This heating process achieves two goals at once. First, it kills the vast majority of pathogens that may be present in the container. Second, it forces out most of the air above the food in the container.
After heating has been completed, the top of the container is sealed. In home canning procedures, one way of sealing the (usually glass) container is to place a layer of melted paraffin directly on top of the food. As the paraffin cools, it forms a tight solid seal on top of the food. Instead of or in addition to the paraffin seal, the container is also sealed with a metal screw top containing a rubber gasket. The first glass jar designed for this type of home canning operation, the Mason jar, was patented in 1858.
The commercial packaging of foods frequently makes use of tin, aluminum, or other kinds of metallic cans. The technology for this kind of canning was first developed in the mid-1800s, when individual workers hand-sealed cans after foods had been cooked within them. At this stage, a single worker could seldom produce more than 100 "canisters" (from which the word "can" later came) of food a day. With the development of far more efficient canning machines in the late nineteenth century, the mass production of canned foods became a reality.
As with home canning, the process of preserving foods in metal cans is simple in concept. The foods are prepared and the empty cans are sterilized. The prepared foods are then added to the sterile metal can, the filled can is heated to a sterilizing temperature, and the cans are then sealed by a machine. Modern machines are capable of moving a minimum of 1,000 cans per minute through the sealing operation.
The majority of food preservation operations used today also employ some kind of chemical additive to reduce spoilage. Of the many dozens of chemical additives available, all are designed either to kill or retard the growth of pathogens or to prevent or retard chemical reactions that result in the oxidation of foods. Some familiar examples of the former class of food additives are sodium benzoate and benzoic acid; calcium, sodium propionate, and propionic acid; calcium, potassium, sodium sorbate, and sorbic acid; and sodium and potassium sulfite. Examples of the latter class of additives include calcium, sodium ascorbate, and ascorbic acid (vitamin C); butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT); lecithin; and sodium and potassium sulfite and sulfur dioxide.
A special class of additives that reduce oxidation is known as the sequestrants. Sequestrants are compounds that "capture" metallic ions, such as those of copper, iron, and nickel, and remove them from contact with foods. The removal of these ions helps preserve foods because in their free state they increase the rate at which oxidation of foods takes place. Some examples of sequestrants used as food preservatives are ethylenediamine-tetraacetic acid (EDTA), citric acid, sorbitol, and tartaric acid.
The lethal effects of radiation on pathogens has been known for many years. Since the 1950s, research in the United States has been directed at the use of this technique for preserving certain kinds of food. The radiation used for food preservation is normally gamma radiation from radioactive isotopes or machine-generated x rays or electron beams. One of the first applications of radiation for food preservation was in the treatment of various kinds of herbs and spices, an application approved by the U.S. Food and Drug Administration (FDA) in 1983. In 1985, the FDA extended its approval to the use of radiation for the treatment of pork as a means of destroying the pathogens that cause trichinosis. Experts predict that the ease and efficiency of food preservation by means of radiation will develop considerably in the future. That future is somewhat clouded, however, by fears expressed by some scientists and members of the general public about the dangers that irradiated foods may have for humans. In addition to a generalized concern about the possibilities of being exposed to additional levels of radiation in irradiated foods (not a possibility), critics have raised questions about the creation of new and possibly harmful compounds in food that has been exposed to radiation.
The astonishing fact about food preservation is that it permeated every culture at nearly every moment in time. To survive ancient man had to harness nature. In frozen climates he froze seal meat on the ice. In tropical climates he dried foods in the sun.
Food by its nature begins to spoil the moment it is harvested. Food preservation enabled ancient man to make roots and live in one place and form a community. He no longer had to consume the kill or harvest immediately, but could preserve some for later use. Each culture preserved their local food sources using the same basic methods of food preservation.
In ancient times the sun and wind would have naturally dried foods. Evidence shows that Middle East and oriental cultures actively dried foods as early as 12,000 B.C. in the hot sun. Later cultures left more evidence and each would have methods and materials to reflect their food supplies—fish, wild game, domestic animals, etc.
Vegetables and fruits were also dried from the earliest times. The Romans were particularly fond of any dried fruit they could make. In the Middle Ages purposely built “still houses” were created to dry fruits, vegetables and herbs in areas that did not have enough strong sunlight for drying. A fire was used to create the heat needed to dry foods and in some cases smoking them as well.
Freezing was an obvious preservation method to the appropriate climates. Any geographic area that had freezing temperatures for even part of a year made use of the temperature to preserve foods. Less than freezing temperatures were used to prolong storage times. Cellars, caves and cool streams were put to good use for that purpose.
In America estates had icehouses built to store ice and food on ice. Soon the “icehouse” became an “icebox”. In the 1800’s mechanical refrigeration was invented and was quickly put to use. Also in the late 1800’s Clarence Birdseye discovered that quick freezing at very low temperatures made for better tasting meats and vegetables. After some time he perfected his “quick freeze” process and revolutionized this method of food preservation.
Fermentation was not invented, but rather discovered. No doubt that the first beer was discovered when a few grains of barley were left in the rain. Opportunistic microorganisms fermented the starch-derived sugars into alcohols. So too can be said about fruits fermented into wine, cabbage into Kim chi or sauerkraut, and so on. The skill of ancient peoples to observe, harness, and encourage these fermentations are admirable. Some anthropologists believe that mankind settled down from nomadic wanderers into farmers to grow barley to make beer in roughly 10,000 BC. Beer was nutritious and the alcohol was divine. It was treated as a gift from the gods.
Fermentation was a valuable food preservation method. It not only could preserve foods, but it also created more nutritious foods and was used to create more palatable foods from less than desirable ingredients. Microorganisms responsible for fermentations can produce vitamins as they ferment. This produces a more nutritious end product from the ingredients.
Pickling is preserving foods in vinegar (or other acid). Vinegar is produced from starches or sugars fermented first to alcohol and then the alcohol is oxidized by certain bacteria to acetic acid. Wines, beers and ciders are all routinely transformed into vinegars.
Pickling may have originated when food was placed in wine or beer to preserve it, since both have a low pH. Perhaps the wine or beer went sour and the taste of the food in it was appealing. Containers had to be made of stoneware or glass, since the vinegar would dissolve the metal from pots. Never ones to waste anything our ancestors found uses for everything. The left over pickling brine found many uses. The Romans made a concentrated fish pickle sauce called “garum”. It was powerful stuff packing a lot of fish taste in a few drops.
There was a spectacular increase in food preservation in the sixteenth century owing to the arrival in Europe of new foods. Ketchup was an oriental fish brine that traveled the spice route to Europe and eventually to America where someone finally added sugar to it. Spices were added to these pickling sauces to make clever recipes. Soon chutneys, relishes, piccalillis, mustards, and ketchups were commonplace. Worcester sauce was an accident from a forgotten barrel of special relish. It aged for many years in the basement of the Lea and Perrins Chemist shop.
The earliest curing was actually dehydration. Early cultures used salt to help desiccate foods. Salting was common and even culinary by choosing raw salts from different sources (rock salt, sea salt, spiced salt, etc.). In the 1800’s it was discovered that certain sources of salt gave meat a red color instead of the usual unappetizing grey. Consumers overwhelmingly preferred the red colored meat. In this mixture of salts were nitrites (saltpeter). As the microbiology of Clostridium botulinum was elucidated in the 1920’s it was realized that nitrites inhibited this organism.
Jam and Jelly
Preservation with the use of honey or sugar was well known to the earliest cultures. Fruits kept in honey were commonplace. In ancient Greece quince was mixed with honey, dried somewhat and packed tightly into jars. The Romans improved on the method by cooking the quince and honey producing a solid texture.
The same fervor of trading with India and the Orient that brought pickled foods to Europe brought sugar cane. In northern climates that do not have enough sunlight to successfully dry fruits housewives learned to make preserves—heating the fruit with sugar.
Canning is the process in which foods are placed in jars or cans and heated to a temperature that destroys microorganisms and inactivates enzymes. This heating and later cooling forms a vacuum seal. The vacuum seal prevents other microorganisms from recontaminating the food within the jar or can.
Canning is the newest of the food preservations methods being pioneered in the 1790s when a French confectioner, Nicolas Appert, discovered that the application of heat to food in sealed glass bottles preserved the food from deterioration. He theorized “if it works for wine, why not foods?” In about 1806 Appert's principles were successfully trialed by the French Navy on a wide range of foods including meat, vegetables, fruit and even milk. Based on Appert's methods Englishman, Peter Durand, used tin cans in 1810.
Appert had found a new and successful method to preserve foods, but he did not fully understand it. It was thought that the exclusion of air was responsible for the preservations. It was not until 1864 when Louis Pasteur discovered the relationship between microorganisms and food spoilage/illness did it become clearer. Just prior to Pasteur’s discovery Raymond Chevalier-Appert patented the pressure retort (canner) in 1851 to can at temperatures higher than 212ºF. However, not until the 1920’s was the significance of this method known in relation to Clostridium botulinum.
Preserving Methods 2
DRYING OR SMOKING
One of the most ancient methods of food preservation is sun- or air-drying. Drying works because it
removes much of the food’s water. Without adequate water, microorganisms cannot multiply and chemical
activities greatly slow down. Dried meat was one of the earliest staple foods of hunters and nomads (people who
constantly moved about). Once fire was discovered, prehistoric cave dwellers heat-dried meat and fish, which
probably led to the development of smoking as another way to preserve these foods.
Drying was a technique used by early American colonists to preserve apples, peaches, pears and apricots
along with some vegetables, meat and fish. Nets woven of hair were used to support the fruit or fish and allow
good air circulation. The food had to be turned frequently and protected from insects, bird droppings and
The tribes of the American Great Plains developed their own method for drying bison meat. This provided
a safe food supply through the long periods between hunting seasons. After eating their fill of the fresh bison
meat, the Indians would take the remaining meat and make pemmican. They would slice the meat thin and hang
it on scaffolds. They hung streamers along with the meat, so they would blow in the wind and keep wolves
away. Once the meat was dry they pounded it and placed it in buffalo rawhide bags about the size of a pillow
case. Sometimes they added dried berries for flavor. The sugar from the berries also helped with preservation.
They poured hot melted marrow in so that it surrounded each particle of meat. Then they sewed the bag shut.
Before the contents became hard from cooling, they walked on it to flatten it. A single sack weighed close to 90
pounds and could be placed across small logs or rocks to keep them off the damp ground.
Salting, which also inhibits bacteria growth, was a preferred method of preserving fish as early as 3500
B.C. in the Mediterranean world, and also was practiced in ancient China. Early American colonists used salt
to preserve pork, beef or fish and some cheese. These foods often provided the only animal protein available
during the winter other than wild game.
Hog butchering was done in the fall, as soon as it was cold enough to chill the carcass rapidly. A certain
amount of the meat was reserved fresh, for immediate use, and some was made into sausage. The rest,
especially the hams (hind legs) and side meat, was treated with salt containing saltpeter (potassium nitrate). This
was stored until it had lost a great deal of water through osmosis. It was then exposed to hickory or fruit-wood
smoke for several days. After that it was hung in a ventilated shed or barn for 6-18 months as it gradually lost
Substances besides salt were also found to slow food spoilage by ancient cultures. The Chinese began
using spices as preservatives around 2700 B.C. Ancient Egyptians used mustard seeds to keep fruit juice from
spoiling. Jars of fruit preserved with honey have been found in the ruins of Pompeii, Italy. Melted fat—as
Native North Americans discovered with pemmican—preserved meat by sealing out air.
As a preservative, sugar acts like salt in reducing water activity enough to prevent the growth of spoilage
bacteria. early settlers used sugar to preserve fruits for winter use. the fruits were boiled with sugar, and the
Food for Keeps
containers were sealed with beeswax or a mixture of candle wax and rosin. Sometimes a piece of paper would
be pasted to the top of the jar with egg white. Sugar was also used as a preservative in meat preparations.
PICKLING OR BRINING
Fruits and vegetables were the most difficult foods to get out of season. Pickling or brining was a fairly
simple way to preserve vegetables without changing their flavor too much. the vegetables were submerged in a
mild salt and vinegar brine in a crock.
Early northern societies quickly learned that coolness as well as freezing helped preserve foods. Microbe
growth and chemical changes slow down at low temperatures and completely stop when water is frozen. PreColumbian
natives in Peru and Bolivia freeze-dried potatoes, while the early Japanese and Koreans freeze-dried
their fish. Water evaporating through earthenware jars was used as a coolant in 2500 B.C. by Egyptians and East
Indians. Ancient Chinese, Greeks, and Romans stored ice and mountain snow in cellars or icehouses to keep
Cold storage was possible in the northern US. root cellars, in which the winter temperatures hovered
between 30 and 40 degrees F., were common. In especially cold weather, a large tub of water was placed on the
floor. This water gave off heat as it turned to ice, keeping the vegetables from freezing. If a family didn’t have
room for a root cellar, a pit served much the same purpose. Vegetables were laid in layers, separated by straw,
and the whole was covered with earth. Ice houses were the first refrigerators. During the winter, these aboveground
houses were filled with blocks of ice cut from streams and lakes and packed in sawdust for insulation.
the ice could then be delivered to homeowners during the spring and summer.
The ice was used to keep dairy products, fish and meat from spoiling. The ice box did not become
popular until the mid-1800s. It had to be recharged frequently with a new block of ice. Although settlers in the
South had access to a more varied food supply year round, they had more difficulty getting ice for short term
protection against the warmer climate. Ice was shipped from Massachusetts to the southern states in the early
19th century, but because of the cost it was available only to wealthier people. Eggs could be stored in the root
cellar or basement. the eggs were dipped in boiling water for 20 seconds then coated all over with butter or
glycerin and packed in sawdust. they would keep this way for 2-3 weeks.
CANNING, FREEZING AND REFRIGERATION
The invention of canning created a revolution in food preservation and availability. The development of
commercial freezing and refrigeration made preservation of fresh meat possible. Refrigerated rail cars, then
refrigerated trucks, also increased the availability of fresh fruits and vegetables.
Microbial contamination of dairy products led to widespread use of pasteurization in these foods. Louis
Pasteur had perfected this method to save the wine industry in France in the late 1870s. It involved heating to
reduce the number of disease producing bacteria.
One of the most recently developed food preservation methods is irradiation. irradiation kills e coli, a
deadly bacteria found in beef and other foods. Irradiation pasteurizes food by using energy, just as milk is
pasteurized using heat. irradiation destroys insects, fungi, or bacteria that cause spoilage and human disease.
During irradiation, energy passes through food much like a ray of light passes through a window. This energy
destroys most of the bacteria that can cause disease yet allows food to retain its high quality. Hospitals use
irradiation to sterilize food for patients with weak immune systems, and astronauts have eaten irradiated foods
for many years. Today’s processed foods retain most of their nutritive value during processing, and in most
cases the loss of nutrients due to processing is less than loss from cooking.
1. Cut very lean, partially frozen flank steak into thin strips, 1 1/2 to 2 inches wide.
2. Dip the strips in teriyaki sauce.
3. Dry the strips, using one of the following methods:
1. Tie small packages of the strips of meat in cheese cloth and hang them in a sunny window. Keep the
packages loose enough so air can circulate around the strips.
2. Every day or so shake the packages gently to make sure they are getting plenty of air.
3. Jerky is ready to eat in about a week, when the meat is shriveled and black and brittle.
1. Arrange the seasoned strips in a single layer on wire racks. Place a piece of aluminum foil on the
bottom of the oven to catch drippings.
2. Preheat the oven to 150 degrees F., and then turn the heat back to 120 degrees F.
3. Place the meat in the oven, leaving the oven door open at the first stop.
4. After five or six hours, turn the strips over.
5. Continue drying at the same temperature for four hours more.
6. Jerky is ready when it is shriveled and black. When cooled, the jerky should be brittle.
1. Arrange the seasoned strips flat and close together on a microwave—safe bacon rack. cover with
2. Microwave at medium low.
3. Turn the strips over, placing the drier strips in the center of the rack.
4. Rotate the rack 1/2 turn, and continue microwaving at medium low for 21 minutes, until the strips are
dry but slightly pliable.
5. Remove to the paper towels.
6. Repeat with remaining strips.
7. Cover the strips with paper towels, and let them stand for 24 hours.
Storage: Wrap the sticks of jerky in plastic wrap, and put them in a container with a tight-fitting lid. Store in the
refrigerator or freezer.
small pieces of fruit—apple, grape, peach, plum, apricot, etc.
1. Line a cookie sheet with a plastic wrap and tape it to the edges. (Do not use wax paper or aluminum foil.)
2. Place small pieces of fruit in a blender. Puree until smooth and thin enough to pour. (Some fruits, like apples
and grapes, make a smoother puree if they are cooked with a little water first.)
3. Pour onto the prepared cookie sheet. Tilt pan to spread evently until it is 1/8- to 1/4-inch thick. Leave at
least one inch around the edges so the plastic wrap can be removed. Make smaller pieces of fruit leather by
pouring puree into small “pancakes.”
4. Dry the fruit leather in a warm oven (140 degrees). Leave the door open 2 to 6 inches. Fruit will dry in 4 to
6 hours. If the oven is too hot, it will begin to cook the fruit. If it is too cool, it may not dry fast enough.
5. Dry it until it is still rubbery. The center should not be sticky. Remove the leather from the tray while it is
still warm. Peel away the plastic wrap, and roll up the leather.
6. Wrap the leather in plastic or put it in an airtight bag or container.
Credit For Content:
World of Microbiology and Immunology 2003
The University of Georgia - National Center for Home Food Preservation
Oklahoma Ag in the Classroom - a program of the Oklahoma Cooperative Extension Service, the Oklahoma
Department of Agriculture, Food and Forestry and the Oklahoma State Department of Education