Like the famed Twinkies, MRE's (meals-ready-to-eat) are believed to last forever.  However, this is where science and science fiction meet.  MRE's were released by the U.S. government as a food source for the military in 1975[i].  MRE's were designed as a self-contained, individual field ration contained in lightweight packaging.  All MRE's are ready-to-eat as is.  No mixing, cooking or water addition.  Previous rations were either canned foods that were heavy to carry or dried foods that required rehydration.   The major innovation in creating MRE's was the tri-laminated metalicized heat stable pouch.   The plastic pouch is lightweight, heat stable, and flexible.  

Quality and Purchase

Initially MRE's were only produced for the military by subcontractors therefore, getting a case or two meant obtaining them by dubious means.  Due to the prevalence of unauthorized sales to civilians, the military began placing a notice on MRE's stating that resale was not permitted.  Because of the demand, there are two different types of MRE’s today; military and civilian.  Many of the military subcontractors simply started making a consumer version of MRE's for sale to the public.  Often the package label looks very similar to the military version.  MREs are widely available both in specialty stores and online.  Specialty stores such as emergency preparedness, survival and camping stores typically carry a variety.  

The quality of MRE's are similar to canned foods.  They are safe to eat providing the metalicized pouch is not compromised.  The military has not studied MRE shelf lives greater than 10 years, so there is no guarantee of their safety after that date.

Packaging

Polyethylene terephthalate (PET or PETE) and foil laminate pouches are exceptional food containers.  The polyethylene (PET) layer is food-grade plastic with no known toxicities and makes up the innermost layer that touches foods.  The foil layer is in the middle and dramatically reduces the transmission of oxygen, CO₂ and moisture through the film.  The outer layer is polyester a tough but non-food grade plastic.  One trade name is Mylar and is often used as a generic name.  Be aware that even though there is a metallic layer in the bag, rodents can easily chew into them.  As soon as the MRE package is opened it is vulnerable to bacteria growth. Military MRE packaging requirements are strict. MREs must be able to withstand a parachute drop from 1250 feet and non-parachute drops of almost 100 feet.  

Storage Conditions

The military stores MRE's in climate controlled warehouses to prolong shelf life.  The colder they are stored, the longer they last.  MRE's should not be frozen, or if they freeze they should be carefully handled, because the foil layer can crack. 

Nutrition and Allergies

A typical military MRE contains between 1200-1300 calories.  The military designed their menus knowing that soldiers in the field should not eat more than 21 days straight of MRE's.  Most MRE's offer complete nutrition including vitamins.  Typically, military MRE's contain 39% carbohydrates, 15 %  protein, and 36% fat.  MRE's procured for military use may or may not have an allergen statement on them.  However, all commercial MRE's made for direct sale to consumers are required to carry both ingredients and an allergen statement.  Most will also have a nutrition facts panel.

Shelf Life

The shelf life of foods packaged in retort pouches is very dependent on storage temperature. For military MRE's the food is required to maintain a minimum shelf life of three and a half years at 27 °C (81 °F), nine months at 38 °C (100 °F), and short durations from −51 °C (−60 °F) to 49 °C (120 °F).   The military has validated MRE safety for up to 10 years.  Beyond that time is not recommended, simply because no data is available.

The following chart represents a general indication of the effects of storage temperature on the shelf life of MRE-type food products.

Use from Storage

Tear open the packaging and enjoy.

References

    [i]   http://www.qmfound.com/mre_tration.htm

    [ii]  http://www.docstoc.com/docs/20093783/flexible-retort-pouch-defects

    [iii] http://www.mreinfo.com/civilian/mre/buying-civilian-mres.html

   [iv] http://www.zdnet.com/news/ebay-sales-of-military-rations-scrutinized/146875

     [v]   http://www.mreinfo.com/civilian/mre/sopakco-sure-pak-12-mre-recall.html

    [vi] http://www.plasticsinfo.org/Main-Menu/MicrowaveFood/Need-to-Know/Plastic-Bev-Bottles/The-Safety-of-Polyethylene-Terephthalate-PET.html

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