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