Most food maintains its edibility for a predetermined length of time before it is no longer safe to consume. The vast majority of food is perishable, including fruits and vegetables as well as dairy products, meat, poultry, fish, and leftover cooked foods. When our distant ancestors discovered this inherent trait, they began to search for methods of delaying decay. As time elapsed and technology and our understanding of biological and chemical processes improved, methods of food preservation also evolved. Currently, science plays a key role in preserving the foods that we consume every day.

Early Preservation Techniques

Before the advent of modern preservation techniques, our distant ancestors had to continuously search for fresh, consumable food. During this time, food had to be eaten almost immediately after it was discovered and harvested. However, humans soon became accustomed to leveraging nature to preserve their food.

For example, peoples living in cold environments discovered the ability to freeze food, a valuable preservation method that is still used today. It is likely that these peoples simply preserved harvested meat by using naturally-occurring ice, which kept it fresh for a longer duration.

preserved chiliThose living in warmer climates utilized the warmth of the sun to dry perishable foodstuffs. By around 12,000 B.C.E., peoples in Middle Eastern and Eastern cultures frequently dried food to preserve its stability. Evidence suggests that later peoples left behind various edible materials that were indicative of their tendency to use drying as a technique to maintain their food supplies.

Romans were another group that favored drying as a preservation technique. During the Middle Ages, they conceptualized and developed “still houses” to dry vegetables and fruits in locations without adequate sunlight. Still houses concentrated the drying effect of heat using fire instead of the sun.

The process of fermentation, the “slow decomposition process of organic substances induced by micro-organisms, or by complex nitrogenous substances (enzymes) of plant or animal origin” was likely discovered around 10,000 B.C.E., although anthropologists are uncertain about an exact timeframe. Many experts attribute the discovery of alcohol, a valuable preservation substance, as a prelude to more elaborate fermentation efforts. The earliest fermented foods were likely naturally fermented fruits, followed by deliberately fermented fruits, grains, milk, meat, and vegetables.

Pickling is the use of vinegar or another acid, such as brine, to kill bacteria and preserve food. This preservation technique, perhaps discovered as a byproduct of fermentation, continues to be used as a viable option for preserving food. The process of preserving foods in honey is another relatively early preservation technique that continues to be used today.

Modern Food Preservation Methods

Some of the earliest methods of food preservation are continued in the present day, such as freezing, drying, and fermenting. However, today, because of many advances in science and technology, food is able to be preserved from harvest to consumption — a relatively long cycle. The invention of refrigeration and freezing technologies, canning, freeze-drying, pasteurization, chemical preservation, and carbonation have contributed to extending the shelf-life of various food products.

However, perhaps the most valuable forms of food preservation are man-made refrigeration and freezing. Refrigerators utilize components that transfer heat from the appliance’s inside to its external environment. This mechanism cools the inside of the refrigerator to temperature ranges just above the freezing point of water (37 to 41 degrees Fahrenheit).

canned peachesHome refrigerators were invented in 1913, and became ubiquitous with the introduction of Freon during the 1920s. Bacteria reproduces at a much higher rate in warmer temperatures; refrigeration drastically reduces this reproduction and expands the consumptive duration of food. Freezers, with inside temperatures below the freezing point of water, halt bacterial growth in many foods.

Chemical food preservation is a very common modern method of preserving food. The process of chemically preserving foodstuffs through curing — salting or smoking — became widely used during the 1800s. Today, curing is done traditionally or with the use of preservatives such as nitrites and other additives. Some of the different classes of chemical preservatives generally used are benzoates, nitrites, and sulphites. Such chemicals either strongly inhibit the growth of, or even kill bacteria.

Unique to the use of chemical food preservation is a contentious, long-standing debate over its safety. The majority of food science experts adamantly support the use of chemical preservatives, citing studies that demonstrate the safety, efficiency and necessity of various chemical preservation techniques.

Pasteurization is a common preservation technique used with liquids — products such as ice cream, fruit juices, milk and beer often undergo pasteurization for preservation purposes. During this process, heat is applied to kill specific bacteria and/or disable enzymatic function. For example, milk is a widely-known pasteurized product. This is usually accomplished by heating the liquid to approximately 145 degrees Fahrenheit for 30 minutes or 163 degrees Fahrenheit for about 15 seconds.

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