PRESERVING. Food preservation conserves food for future use. Most of the basic processes have been employed throughout the world for millennia. The primary methods of salting, canning, drying, pickling, smoking, salting, fermenting, cold storage, and freezing all provide an extreme environment in order to stabilize the food for later use. Although most of these methods are used both commercially and in the home, the basic techniques are the same.
Early Methods of Preservation
The idea of preserving food for future consumption was probably first practiced by storing it in a secure place. Original practices mirrored natural processes, such as cold storage, freezing, drying, and even fermentation, which can naturally occur in fruit. Food preservation is evidenced in the archaeological record and in early written records, which indicate the use of salt, snow, smoke, pickling, drying, and fermenting. Ancient Mesopotamia, Egypt, Greece, and Rome all practiced many of these methods of food preservation. Evidence from a Chinese tomb dating prior to 2,000 years ago gives instructions on inscribed bamboo for salting, drying, and pickling. Sixteenth-century records from the observations by the European conquerors of the Maya indicate the use of smoking to preserve peppers and other foods. Methods of preservation like sun drying, smoking, and salting might have been used very early on to preserve the most perishable types of food, such as fish.
Salt, naturally occurring in deposits or as evaporated seawater, could have been dissolved in water as a brine, or in combination with other processes, like drying and smoking, could have preserved many foods. Some foods were not edible in their natural state, like certain tubers or olives, and would have required brining. Grains in particular, once harvested, were probably kept for consumption throughout the year and as protection against the failure of a future harvest. Storage in a dry and cool environment would have prevented molds and sprouting of grains. Fermentation of grain to make beer and of grapes to yield wine can preserve a large and perishable crop.
Early food preservation included simple "banking" in pits, which were dug in the ground and lined with various substances like wood, straw, and leaves to create a barrier between the soil and the food. Caves and storage vessels that were buried or sunk into the ground were also used to create a secure storage environment for the food. Food could be stored in skins, baskets, pottery vessels, or special structures built for certain commodities like grain. Liquids required a much more specialized container, and large supplies of certain commodities, like olive oil, beer, and wine, while difficult to transport, were valuable trade items, and required secure seals to protect the quality of the contents.
Pests, insects, damage from weather or moisture, molds, fungus, decomposition, or a combination of these factors lower the quality of or even destroy the food, and these factors had to be taken into account. Whether the food preserved is being held to guard against future crop or harvest failures, for trade or barter for other commodities, or to divy out certain foodstuffs as part of the yearly diet, the quality of the food preserved had significant impact upon the future quality of life.
Canning refers to a technique used both commercially and in the home to preserve food in sealed containers. In the early twenty-first century, metal cans are used commercially and glass jars are used in the home. The concept of preserving foods by cooking them and then sealing them in a container is ancient. Olive oil, lard, wax, pitch, clay, and skin have all been used to seal vessels containing food, but are not very reliable. In the late eighteenth century, France offered a monetary award for a method that could be used to preserve food for soldiers. After years of experimentation, Nicholas Appert successfully used sealed glass jars, whose contents had been thoroughly cooked in a water bath, to create portable and potable food. He was awarded the prize in 1809 for his work and went on to publish his findings in "L'art de conserver pendant plusieurs années toutes les substances animales et vegetales" (The art of preserving all kinds of animal and vegetable substances for several years). In 1810, Englishman Peter Durand received a patent for the same process but included tin containers as well as glass.
Tin containers had been used for food storage previously, but it was the combination of the water bath and the sealed container that was so successful. Initially made by hand, tin-plated cans sealed with lead solder were used. By 1819 the Arctic explorer William Edward Parry had included canned foods with the expedition supplies, but the discovery in the 1980s of some of the bodies of those lost on John Franklin's last Arctic expedition in 1847 and their analysis in the 1980s and 1990s indicates that they were suffering from lead poisoning from the lead seals in food cans. Food cans manufactured in the United States have not used lead solder since the mid-1990s, but canned food products from other countries could contain lead solder.
In the United States, various individuals worked on streamlining tin can production, improving the methods of canning various foods, like corn, tomatoes, and lobster. During the mid-nineteenth century in the United States, both commercial canning and home canning expanded, driven by the demand for product by the westward expansion of settlers. The armies of the Civil War used canned goods. Another significant milestone was canned condensed milk, which provided canned milk that was safe to drink, and was developed by Gail Borden in the mid-nineteenth century.
As more foods became available in cans, home cooks "canned" in glass a wide variety of products using basically the same techniques. In both commercial and home canning critical factors were sufficient temperature, sterile containers, and an effective seal. John Mason patented a glass jar with a screw cap to seal it in 1858; numerous patents followed for a reliable and effective seal. The consequences could be illness and even death from bacteria that could grow inside the container, generally the naturally occurring botulism bacteria (Clostridium botulinum). Invented in the early twentieth century, the new and most common jar closure used today has two parts that separate the jar cover from the threaded ring. Commercial canned goods created a dependable and transportable food, and are used extensively by consumers all over the world. Canned soup, tuna, juice, corn, tomatoes, and condensed milk are some of the most popular canned foods. In the United States, the cooperative agriculture extension service of the USDA is a source of accurate and inexpensive advice on all types of home preserving. Home canning has diminished in the United States as families moved away from their source of food, but in a 1996 survey, 56 percent of all U.S. households said they had canned in the past, of whom 28 percent had canned within the last two years. Although pressure canners are considered safer, many still use the conventional water bath for home processing.
Drying occurs naturally with food left in the sun, or on the vine, like beans, or grapes. Some foods, like apples and tomatoes, are generally cut into smaller pieces for drying, a practice which allows the moisture to uniformly evaporate. Herbs are frequently dried whole and on the stem. Low humidity, heat, and air circulation are important so that mold does not occur. Meats and fish can be dried to the point of extreme desiccation, resulting in a product usually called jerky. Drying racks, screens, bags, strings, and bunches can be dried outdoors or in a warm dry spot indoors. Ovens or specialized equipment like dehydrators can be used to create the low temperatures necessary. Once dried, foods can keep for up to a year in a cool and dry environment. Dried foods are sometimes additionally smoked or salted.Dry storage is usually used for grains, whole vegetables, and fruits like potatoes, onions, carrots, apples, pears
Fermenting produces beverages like wine and beer and foods like cheese and bread. Fermentation can occur naturally and with naturally occurring yeasts, or lactic acids. Early records in the Sumerian language indicate the manufacture of both beer and bread. Ancient wine making uses yeast and bacteria to transform raw material into the fermented beverage. Fermentation is the result of enzyme activity, naturally occurring proteins present in the food, or can be introduced into it. Sauerkraut and fermented vegetables, like the Korean dish kimchi, are produced with lactic acids. The cabbage, vegetable, or mixture is salted and placed in a container where it will ferment, creating an acid environment that will preserve it. This fermentation process is called pickling, just as the use of vinegar and the use of brine are also called pickling.
Vegetables can be very difficult to preserve without processing, but a wide variety of vegetables can be preserved by the addition of salt, after which the juices then drain from the vegetables and ferment. Certain sausages, vegetables, yogurts, and cheeses are all preserved by fermentation. Louis Pasteur's wide-ranging research, which included studying the fermentation process in wine and beer making, led to pasteurization and also to the theory that bacteria existed. The presence of harmful bacteria explained why food preservation had to follow very strict aseptic guidelines, or the food could become spoiled, inedible, or at its worst deadly.
The origins of yogurts and cheese are frequently explained as the result of milk being stored in a skin and warmed, which caused the milk to ferment, and separate into solids and liquids, or curds and whey. Through the use of lactic acid, salt, and heat, and by draining the liquids, cheese is created. By draining, application of pressure to remove the moisture, and by aging cheese can be held for years. Butter can also be preserved with salt. The quantity of salt necessary to preserve butter was such that early instructions required that the butter be washed before use. Unsalted butter is more perishable and has a different flavor.
Cold storage or refrigeration slows down decomposition of food. Initially, cold storage used natural snow and ice usually kept below ground and covered with straw, or branches. Snow was usually compressed to slow melting. In much of the ancient world, snow and ice were harvested, stored, usually in pits, and used in the summer.
Melting and storage were continuing problems. Much time and effort were devoted to solving these problems over the centuries, but it was in the nineteenth century that many technological advances occurred. In 1803, a Maryland farmer patented an insulated icebox using layers of insulation with charcoal dust. Icehouses were generally below ground structures, although circular brick ones were also used, and filled with layers of ice. In 1827, a more efficient horse-drawn ice cutter was invented for cutting natural ice off lakes and rivers. By the 1840s refrigerator railroad cars were in use in the United States. Around that same time various advances were made in artificially creating ice and refrigeration. John Gorrie, a physician in Florida, received a patent for ice manufacture in 1851. The technology existed, but the product was too expensive compared to natural ice. However, after the blockade of the South and the Civil War, artificial icehouses began to open. For example, the steam-operated Louisiana Ice Manufacturing Company opened in 1868, selling ice for $1.75 for a hundred pounds. By the 1880s ice plants were located throughout the United States, but natural ice was still sold as well. In the twentieth century, ice became universally accessible. In 1913, the first home refrigerator became available and by the 1940s, 56 percent of all U.S. kitchens had electric refrigerators.
Freezing food originally took advantage of natural freezing, or below freezing temperatures, but artificially freezing food is an ancient practice as well. Frozen foods are quite stable, although flavor and texture may change. Experiments in compression and condensation led to mechanized ice production, and improved efficiency eventually dropped the price of artificial ice, so it was competitive with natural ice. Home machinery initially stored the ice needed to cool the food. Today, automatic ice and frozen food storage are present in most homes. Clarence Birdseye is generally credited with creating the commercial market in frozen foods, based on his experience with fish in the Arctic. After some years of experimentation mainly with fish, he had perfected his process by 1924, and coupled with advances in freezer cases in stores, frozen foods became widely available.
Freeze-drying is thought to have originated in Peru where the potato has been cultivated for about nine thousand years. At high altitudes, the potato harvest was spread on the ground and exposed to extreme cold and then pressure was applied to remove all moisture. Like other dried products, water is used to reconstitute the dried potato. Freeze-dried coffee was developed in the 1930s, and the United States space program used freeze-dried foods because of their light weight and stability for the astronauts' meals.
Irradiated food is exposed to radiation from gamma rays or electron beams or X-rays to kill bacteria, insects, and parasites and reduce spoilage. NASA irradiates food used by its astronauts. Irradiation of food began in 1963, and in addition to the United States, a variety of countries use irradiation for food, including Russia, France, China, and South Africa. Currently, some fruits, vegetables, spices, and meats are irradiated and must be marked with an international symbol called a radura and sometimes a statement such as "irradiated to destroy harmful microbes."
Like many of the terms used in food preservation, the term "pickling" can mean several things. It can be used for preserving vegetables, fish, or meat with an acetic acid, or a vinegar. It can also be used to refer to a salt solution, or brine. Generally, it is used to describe the use of vinegar, spices, and salt to preserve vegetables, herbs, and fruits.
Salt is used as a dry packing material or dissolved in water as brine. In both cases it removes liquid from the meat, fish, plant, or dairy product, and prevents decay. To salt for preservation is to use salt to remove the moisture from the fish, meat, or vegetable. The brining method uses salt that has been dissolved in water. The salt is sometimes mixed with sugar and spices. Fish may be hung to dry afterwards, and can then be smoked. Salted codfish is still popular and widely available in spite of pressure on the diminishing population in the Atlantic Ocean. Cuts of meat can remain in the dry cure for a period of time based on weight, usually about twenty-five days, and then are frequently smoked.
Brining is a similar process, with water, salt, sugar, and spices as usual parts of the brine. In brining, it is very important that the meat stays below the surface of the liquid. Time in the brine is related to weight, and the brine must be checked regularly to ensure that it is stable. Temperature fluctuations or insufficient salt can result in the loss of the ability of the brine to preserve the food, and decomposition can begin. The first evidence of this is usually the formation of a mold or "scum" on the surface. Early directions all indicate that the barrels or containers should be checked daily for this reason. Vegetables can also be preserved in brine, or with a dry salt coating. Anchovies, butter, capers, lemons, and herbs, even eggs are also commonly preserved with salt. Salt is also used to produce extremely concentrated and highly flavored sauces, particularly of soy, and/or fish, which have been in use since antiquity and were extremely important for flavor. The Romans had garum and other sauces, and the Chinese had soy sauce, for example. These condiments have modern counterparts in soy sauce, hot pepper sauce, fish sauces, and Worcestershire sauce. The purpose of all of these concentrated sauces, ancient and modern, is to carry an extremely dense flavor and saltiness into foods. Sweet flavors, in preserved fruits, were intensified by the combination of sugar and concentration through cooking.
Smoking is frequently used in combination with salting. For example, the ancient Mayans preserved chilis, as well as fish and meat, by smoking; in his treatise "On Farming," Cato describes salting and smoking a ham. Smoking takes two basic forms, hot and cold. In cold smoking, the purpose is to impart flavor, not to cook the food, whereas in hot smoking, the appropriate temperature for the fish or meat is necessary to "cook" it.
Early sweeteners included honey and syrups made from grapes, figs, or dates. Sugar made from cane was costly, but it became more available by the sixteenth century when the sugar plantations that were planted in the Caribbean and South America became major producers. Beet sugar was also in production by the nineteenth century. In preserving with sugar, fruit and a sweetener are cooked together until thickened and then packed into containers. Sometimes are included pieces of the fruit, and other times the mixture is strained and just the resulting liquid is kept. Whole fruits can also be cooked in syrup, until they have completely absorbed the sugar, and then left whole and eaten as a confection.
Our sense of taste identifies flavors as sweet, sour, salty, bitter and some say, umami (or savory). The major preservation techniques utilize these very flavors, creating the core of our palate.
See also Beer; Birdseye, Clarence; Cheese; Fermentation; Fermented Beverages Other than Wine or Beer; Fish, Salted; Fish, Smoked; Food Safety; Frozen Food; Jam, Jellies, and Preserves; Meat, Salted; Meat, Smoked; Microorganisms; Packaging and Canning, History of; Pasteur, Louis; Soy; Storage of Food; Wine.
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Daphne L. Derven
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