A retort pouch is a form of advanced food packaging that has, in many instances, replaced the need for canning. The concept was invented by the United States Army in 1978 as a method of storing rations for troops, known as Meals, Ready-to-Eat (MREs), but it has since been adapted to a wide array of consumer products, even including some pet food snacks. The retort pouch consists of multiple layers of plastic and aluminum, or gold-colored metal foil laminate. It is so durable and puncture resistant that it has earned the name “flexible can.” Some even have see-through windows so that the consumer can view the contents before buying the product.
Retort pouch food storage is a form of aseptic processing, or sterilization of food. Such packaging is often confused with vacuum packaging, which looks the same, but has some important differences. In vacuum packaging, a food such as salmon is typically heated and then packaged, where all air is removed from the package. This retards the growth of most bacteria that require oxygen, and destroys other bacteria in the heating process. There are varieties of dangerous bacteria that can survive the process however, such as Clostridium botulinum which causes botulism, and can grow in the absence of air.
This limitation of vacuum packaging makes it necessary for vacuum-packed foods to be refrigerated after opening. They also have a shorter shelf life in general than the retort pouch. In the processing of foods such as salmon, the pouch itself can withstand higher heating temperatures. It is heat-processed under pressure at levels above 230° Fahrenheit (110° Celsius) at which all bacteria are destroyed. Foods packaged in this type of pouch, therefore, do not have to be refrigerated before opening, and can be stored in the same manner as traditional canned goods.
One of the additional advantages that a retort pouch offers is that the preparation of the food is done by heating it within the pouch. The steam generated from water in the food kills off bacteria. No nutrient value is lost in the process of cooking the food either, as it is entirely self-contained.
Some retort pouch designs also contain what is known as a flameless ration heater (FRH), which is an extra exterior pouch. Water is added to the FRH to create an exothermic reaction, and reheat foods to a temperature of 100° Fahrenheit (38° Celsius) in about ten minutes. The FRH was introduced into MREs in 1992 for the US military, and can now be purchased by consumers for heating camp food.
The retort pouch is an extremely strong and versatile method of safely storing food. It weighs less than traditional vacuum-packed canned goods, doesn't require the use of precious metals in large quantities, and is more portable. Its popularity in Asian nations has led to it being used for storing a wide variety of Chinese-style dinners of various fish and vegetable meals.