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Natural Food Preservation
Food products begin to decompose immediately after they are harvested, so humans have had to compensate for this in order to preserve food for future use. The advent of chemical preservatives is relatively recent, so humans have found multiple processes that delay the decomposition.

Smoking
Wood smoke has been traditionally used to preserve meat. "The smoke contains a number of antimicrobial compounds such as phenols, syringol, and guaiacol and their derivatives as well as carbonyls, catechol as well as naphthalene derivatives." Msagati, T. (2012). “The Chemistry of Food Additives and Preservatives” These compounds aid in the drying and preservation of meats and other foods.

Drying
Drying is one of the oldest techniques used to hamper the decomposition of food products. As early as 12,000 B.C. Middle Eastern and Oriental cultures were drying foods using the power of the sun. Vegetables and fruit are naturally dried by the sun and wind, but in the Middle Ages, "still houses" were built in areas that didn't have enough sunlight to dry things. A fire would be built inside the building to provide the heat to dry the various fruits, vegetables, and herbs.

Freezing
Any culture that has freezing temperatures for at least part of the year made use of them for food preservation. Less than freezing temperatures, like in caves, cellars, and cool streams, can prolong storage time as well. "Freezing and chilling slows down both the metabolic and enzymatic activities for the microbes, thus discouraging their growth and multiplication. Chilling and freezing only slows down the growth; the processes do not kill the pathogens.  This approach needs to be coupled with other preservative means to effectively preserve foodstuffs." Msagati, T. (2012). “The Chemistry of Food Additives and Preservatives”

Fermenting
Fermentation happens when microorganisms process the starch-derived sugars into alcohol. Not only can fermentation produce alcohol, but it can also be a valuable preservation technique. Fermentation can also make foods more nutritious and palatable. For example, drinking water in the Middle Ages was dangerous because it often contained pathogens that could spread disease. When the water is made into beer, it kills any bacteria in the water that could make you sick. Additionally, the water now has the nutrients from the barley and other ingredients, and the microorganisms can also produce vitamins as they ferment.

Pickling
Pickling is the process of preserving food in vinegar or other acid. "Lowering of the pH environment where food is kept may discourage the multiplication of microbial cells, since this also suppresses the metabolic and enzymatic activity of the microbial pathogens."

Curing
The earliest form of curing was actually dehydration, and many cultures used salt to help this process. In the culinary world it was common to choose raw salts from various sources (rock salt, sea salt, etc). More modern "examples of salts that are used as preservatives include sodium chloride (NaCl), sodium nitrate NaNO3 and sodium nitrite (NaNO2). Even at mild concentrations (up to 2%) sodium chloride (which is present in many food products) is capable of neutralizing the antimicrobial character of natural compounds." Msagati, T. (2012). “The Chemistry of Food Additives and Preservatives”

Sugar
The earliest cultures have used sugar as a preservative, and it was commonplace to store fruit in honey. Similar to pickled foods, sugar cane was brought to Europe through the trade routes. In northern climates without sufficient sun to dry foods, preserves are made by heating the fruit with sugar. "Sugar tends to draw water from the microbes (plasmolysis). This process leaves the microbial cells dehydrated, thus killing them.  In this way, the food will remain safe from microbial spoilage." Msagati, T. (2012). “The Chemistry of Food Additives and Preservatives”

Canning
Canning is a preservation process that involves jarring food, and then heating the jars until the microorganisms are destroyed and the enzymes are inactivated. This heating and cooling of the jar forms a vacuum seal, which prevents other microorganisms from contaminating the food. Canning is by far the newest form of food preservation, discovered[ by Nicolas Appert in the early 1790's. This French confectioner discovered that applying heat to sealed glass bottles preserved the food inside. By 1806, this process was used by the French Navy to preserve meat, fruit, vegetables, and even milk. Although Appert had discovered a new way of preservation, it wasn't understood until 1864 when Louis Pasteur found the relationship between microorganisms, food spoilage, and illness.

Chemical Preservatives and Modern Debate
The preservation of foods has evolved greatly over the centuries, and has been instrumental in increasing food security. The use of chemical preservatives (other than traditional oils, salts, etc.) in food began in the late 19th century, but were not widespread until the 20th century as governments began regulating their use, and exploring their risks and benefits. As food additives for preservation came into widespread public consumption, certain factions of health advisers and concerned parents began to question the side effects of these chemicals. Consumers found that the additives were helpful and allowed for bulk buying and storage, while manufacturers enjoyed their profitability, as they could extend the shelf life of a product and therefore allow for much more long-distance shipping of foods. However, there is increasing debate in popular consumption of preservatives as there is increasing demand for products being natural rather than chemically preserved. Of course, the definition of 'natural' is much disputed.

The major debate that goes on today about preservatives has to do with their effect on the health of consumers. Anti-preservative advocates argue that preservatives should be avoided in favor of more natural options, while those who support preservative use maintain that chemical preservatives have no negative effects on the consumer, and hold many benefits for increasing food supply. The compendium of studies related to preservative effect on health have been largely inconclusive, as various studies have had conflicting findings, and many have had problems with keeping children's diets consistent or well-documented. One of the more prominent arguments against preservative usage asserts that preservative consumption can be linked to ADHD in children. Other claims include health risks that are closely related to sugar and fat intake - which makes their specific cause difficult to identify. In 1982 the American National Institutes of Health issued a statement saying that there is no scientific evidence to substantiate claims that chemical preservatives cause hyperactivity in children. They have since removed this statement, not connecting themselves to either side of the debate.

The global use of food preservatives varies greatly depending on country. Many developing countries that do not have strong governments to regulate food additives face either harmful levels of preservatives in foods, or a complete avoidance of foods that are considered unnatural or foreign. These countries have also proven useful in case studies surrounding chemical preservatives, as they have been only recently introduced. This issue of global circulation is also complicated by relationships between countries and importations from wealthy countries that negatively impact the profits of small farmers. In urban slums of highly populated countries the knowledge about contents of food tends to be extremely low, despite consumption of these imported foods.