The Meal Ready-To-Eat Retort Pouch and Component Packaging
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The MRE (Meal – Ready to Eat) Retort Pouch
and Component Packaging
OUTLINE
I. Abstract
A. The Meal, Ready-to-Eat
B. Nutrition
1) Caloric value
2) Recommended Daily Allowance
II. Introduction to the Retort Pouch
A. Make-up of the pouch
1) Tri-laminate MRE retort pouch
2) Manufacturing specification
3) Thermo-stability requirements
B. Laminate qualities
1) Three layers and object of design implementation
C. Possible problems with military retort pouch use
1) Punctures, tears, holes
2) Outer carton use and integrity boost
III. Difference between retort pouch and non-retort pouch
A. Adhesive use on seals
B. Types of food and retort pouch use
C. Other packaging use in MRE
IV. Retort Pouch Printing
A. Required Markings
B. Soldier or inspector use of markings
V. Defects Likely to Occur
A. Delamination
B. Inspection for defect pouches
VI. Design Improvement and Testing
A. Laboratory testing of pouch suitability
B. Pouch component shelf-life
1) Freezing effects
2) Dry storage shelf-life
3) Refrigerated shelf-life
VII. Summation
A. Combat soldier acceptance
B. Field feedback
The Meal, Ready-To-Eat (MRE) has been specially designed to sustain an individual soldier in heavy activity such as during actual military operations when normal food service facilities are not available. The MRE is a totally self-contained operational ration consisting of a full meal packed in a flexible meal bag. The full bag is lightweight and fits easily into the soldiers military field clothing pockets. The contents of one MRE meal bag provide an average of 1250 kilocalories (13 % protein, 36 % fat, and 51 % carbohydrates). It also provides 1/3 of the Military Recommended Daily Allowance of vitamins and minerals as determined by the Surgeon General of the United States.
Most of the food components of the MRE are packaged in flexible packages. Some of the packages are the same or very similar to those used for previous types of operational ration components, but others are newer forms of packaging technology such as the vacuum packed tri-laminate, non-retortable pouch, and the tri-laminate, retortable pouch. Since almost all of the primary and secondary components of the MRE are packaged in tri-laminate pouches, these will be the primary presentation focus.
The retortable pouch, often referred to as the flexible can, is what brought the MRE into production in 1980. It is fabricated as a three-ply laminate consisting of, from inside to outside, a 0.003 to 0.004 inch thick polyolefin layer, a 0.00035 to 0.0007 inch thick aluminum foil layer, and a 0.0005 inch thick polyester layer. When fabricated in accordance with military specifications, it should be able to withstand thermal processing, or retort processing, and a wide temperature range sufficient enough to prevent package damage during transportation and storage. Food packaged in a conventional can must be cooked approximately twice as long as food contained in a retort pouch, as well. To sterilize the food contained in either form of packaging, it must be brought up to approximately 245o F and kept there for a specified period of time. Retort packages have a thin profile and a high ratio of surface area to volume. Heat penetrates the food much more quickly when it only has to reach the inside of an approximately half-inch-thick mass, rather than a much larger mass in a round can.
Coloring is also applied to either the exterior or interior surface of the polyester layer. While the pouch is considered a “tough” package, it is not indestructible. The strength of the pouch and its resistance to damage comes from its tri-laminar structure. Strength of the pouch has always been an issue for the Military, and its difficult for some to understand that plastic can be as strong as steel, as metal cans are usually associated with strength.
Each of the three laminas has its own individual qualities that contribute to the success of the pouch. A single laminate layer is not capable of providing all the qualities required of a package that undergoes the rigors of military handling, storage, and distribution. The outer layer of polyester provides strength and resistance to tearing. The middle layer of aluminum foil laminate provides an almost absolute barrier to the transfer of gases, especially oxygen, and water vapor between the environment and the product in the pouch. The inner layer of polyolefin provides an inert product contact surface and is a heat sealable material essential for attaining a hermetic seal. The tri-laminar structure is so reliant on the cooperation (synergism) of the three layers, that the failure of one or more layers, including delamination