Retort bags are a durable and advanced form of food packaging that can replace canning. They consist of multiple layers of plastic and metal foil and use aseptic processing to sterilize food. Unlike vacuum packaging, retort bags can withstand higher heating temperatures and have a longer shelf life. They also allow for cooking inside the bag and can include an external flameless ration heater. Retort bags are popular in Asian nations for storing Chinese-style dinners.
A retort bag is a form of advanced food packaging that has, in many cases, replaced the need for canning. The concept was invented by the US Army in 1978 as a method of storing rations for troops, known as Meals, Ready-to-Eat (MRE), but has since been adapted to a wide range of consumption, including some pet snacks. The retort bag consists of multiple layers of plastic and aluminum or gold-colored metal foil. It is so durable and resistant to punctures that it has earned the name “flexible can”. Some even have transparent windows so that the consumer can view the contents before purchasing the product.
Food storage in retort bags 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 oxygen-demanding bacteria and destroys other bacteria in the heating process. However, there are varieties of dangerous bacteria that can survive the process, such as Clostridium botulinum which causes botulism and can grow in the absence of air.
This limitation of vacuum packaging makes it necessary to refrigerate vacuum-packed foods after opening. They also have a shorter shelf life overall than the retort bag. In processing foods such as salmon, the pouch itself can withstand higher heating temperatures. It is heat treated under pressure at levels above 230° Fahrenheit (110° Celsius) at which all bacteria are destroyed. Therefore, food packaged in this type of bag does not need to be refrigerated before opening and can be preserved like traditional preserves.
One of the additional benefits that a retort bag provides is that the preparation of the food is done by heating it inside the bag. The steam generated by the water in the food kills bacteria. No nutritional value is lost in the cooking process of the food either, as it is completely self contained.
Some retort bag designs also contain what is known as a flameless ration heater (FRH), which is an additional external bag. Water is added to the FRH to create an exothermic reaction and heat food to a temperature of 100° Fahrenheit (38° Celsius) in approximately ten minutes. FRH was introduced in MREs in 1992 for the US military and can now be purchased by consumers to reheat camp food.
The retort pouch is an extremely sturdy and versatile method of safely storing food. It weighs less than traditional vacuum-packed products, does not require the use of precious metals in large quantities, and is more portable. Its popularity in Asian nations has led it to be used to store a wide variety of Chinese style dinners of various fish and vegetable dishes.
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