Early methods of food preservation

The preservation of harvested and prepared food for future consumption is one of the oldest practical arts, a necessity that developed from the sheer need to survive in a hostile environment where fresh food was not always available. Techniques for drying foods date back to ancient times, when fruits and vegetables were dried in the sun or on an open stove. Without water present, the dehydrated foodstuffs would not support microorganisms and therefore did not spoil. By 1000 BC, the Chinese were using salt, spices, and smoking to create a sterile environment for different food products. Salt also acts as a dehydrating agent and is particularly useful for fish and meat. Salted meat served explorers and military forces well because of its stability and portability, and it was a technique that lasted into the twentieth century.

It was also discovered very early that making cheese could preserve dairy products, grape juice could be fermented into wine that would last for years at normal temperatures, and even cabbage could be preserved by converting it to fermented sauerkraut. North American Indians made pemmican by drying the meat of buffalo or deer and then mixing it with a large amount of fat. This was effective because the fat presumably excluded oxygen.

Food preservation changed significantly, however, in the early 1800s, when the Frenchman Nicolas Appert made "the seasons stand still" by inventing a technique to preserve foods in glass jars. Appert opened a factory at Massy but also described his process for anyone to follow. Appert had discovered that unwanted bacteria were destroyed by placing the jars in boiling water for a specific time period depending on the food and then sealing the jar under these sterile conditions. Although Appert preferred glass because he thought it was the best for keeping out oxygen, others soon followed with metal containers, and the modern canning industry was born.

The Incas stored their potatoes and other foods at the high altitudes where they lived in the Andes Mountains. The food froze at these cold temperatures, and because of the reduced atmospheric pressure, the water dissipated more quickly than it would have at sea level. Early in the twentieth century this process was more carefully developed when frozen foods were placed in a vacuum, allowing the frozen water crystals to sublime directly from the solid to vapor form, where they could be easily removed. Freeze-dried foods can be stored for a long time and are easily reconstituted if desired. This process was slow to find any commercial application until the 1930s, when freeze-dried coffee was first manufactured in Switzerland. During World War II some troops were supplied with freeze-dried orange juice, and freeze-dried blood plasma was carried by medics into the front battle lines. Several hundred food products have been commercially freeze-dried since 1960.

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