- Sara Thompson
Science of Food Preservation
By Sara Thompson
Special to the Enterprise
All life needs some form of gaining energy to replace what is used for living. For most organisms, this is simply eating food. Most everything that gets eaten has bacteria with it. Some bacteria are helpful, most animals have some in their digestive tracts to help with the breakdown of foods, but some bacteria, or too much of the beneficial ones, can make animals sick. Bacteria is what causes food to spoil. Food preservation is when we try to slow down the spoiling process.
It has long been known that keeping food cool will slow spoiling. Food stores have been found deep in caves or in dug-out cellars. Cool storing works well for people who have settled in one area, but nomadic people needed to find alternative ways of food preservation.
Cooking food can help destroy bacteria prior to eating, but shortly after it will begin to grow again. An early preservation method for meat is smoking. Smoked meat will last longer than cooked meat and was a common method after hunting or butchering raised animals. This was common for nomadic people who could pack smoked meat when on the move and between hunting trips.
Another early form of preservation was salt packing. The salt would remove the water from meats and other foods. Without water, bacteria could not grow as fast, and this allowed the food to last longer, albeit very salty.
In the early 19th century canning was invented by Nicolas Appert, a French chef. Once the food is added to a metal can or glass jar, it is sealed and submerged into boiling water. The boiling water kills the bacteria and cooks the food slightly. How long it is submerged depends on what is being canned, as bacteria on some foods can withstand boiling longer than others. Once removed from the water the hot air will escape, taking any remaining oxygen with it. This process causes the lid to pull close and form a seal on the can. Because the bacteria was killed during boiling and the sealed can does not allow any air in the food will stay fresher longer, up to several years, but using within one is recommended. Once a can or jar is opened exposure to the air will allow bacteria to grow once again. This is one reason many shelf-stable items say “refrigerate after opening”. Once opened, keeping the contents cold will continue to preserve the contents.
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