Canned salmon

Canned fish are fish which have been processed, sealed in an airtight container such as a sealed tin can, and subjected to heat. Canning is a method of preserving food, and provides a typical shelf life ranging from one to five years.

Fish have a low acidity at levels where microbes can flourish. From a public safety point of view, foods with low acidity (a pH more than 4.6) need sterilization under high temperature (116-130 °C). To achieve temperatures above the boiling point requires a method of pressurized cooking which is provided by the containment within the can. After sterilization, the containing can prevents microorganisms from entering and proliferating inside. Other than sterilization, no method is perfectly dependable as a preservative. For example, the microorganism Clostridium botulinum (which causes botulism), can only be eliminated at temperatures above the boiling point.

Such preservation techniques are needed to prevent fish spoilage and lengthen shelf life. They are designed to inhibit the activity of spoilage bacteria and the metabolic changes that result in the loss of fish quality. Spoilage bacteria are the specific bacteria that produce the unpleasant odours and flavours associated with spoiled fish.

The "father of canning" is the Frenchman Nicolas Appert. In 1795, he began experimenting with ways to can fish in jars and then he placed the jars in boiling water. During the first years of the Napoleonic Wars, the French government offered a 12,000 Franc prize to anyone who could devise a cheap and effective method of preserving large amounts of food. The larger armies of the period required increased and regular supplies of quality food. Appert submitted his invention and won the prize in January 1810. The reason for lack of spoilage was unknown at the time, since it would be another 50 years before Louis Pasteur demonstrated the role of microbes in food spoilage. However, glass containers presented challenges for transportation. Shortly after, the British inventor and merchant Peter Durand patented his own method, this time in a tin can, creating the modern-day process of canning foods.

...
Wikipedia