MREs (Meal, Ready-to-Eat) were born on Earth, but grew up on Apollo flights to the moon, in Skylab floating workshops and on every U.S. Space Shuttle flight from Enterprise to Atlantis. In the 1970s retort pouches* (the popular name for thermostabilized, laminated food pouches named after the retort cooker ) were put to their first real test by the U.S. Space Program. The Program was looking for delicious, easy to prepare, "normal" food that wouldn't increase human stress the way that freeze dried food and "toothpaste tube food" did. More than any other technology, retort pouches have satisfied the Program's needs. And so, over 20 years ago, retort pouches found a home at NASA, where all their unusual characteristics were much appreciated and they have been successfully feeding astronauts in flight and on the moon ever since.
*Retort describes a thermostabilization (meaning heat-treated) process -- like canning. The pouch is made out of several layers and is like a flexible can. It has better storage and distribution qualities than a can, without the weight or need for a can-opener. The pouch is filled with the food product then sterilized in big pressure-cooker-like equipment. This process gives the product along shelf-life and helps retain natural juices and flavors.
In the 1980s the U.S. military research labs, which had hatched the pouch technology in the first place, took the lead in its use and development. They enabled the U.S. Military to upgrade its entire field ration program to retort pouches, from the earlier, less workable technologies of canning and freeze drying. Over the past 10 years these high tech research labs have continually upgraded the taste and nutritional profile of the meals. For over a decade our military has depended on MREs for its field ration requirements. Tens of millions of MRE "full meals" have been produced and eaten. They have gone to Grenada, to the war on drugs, to fight forest fires in Alaska, and to feed the troops in "Desert Shield" and Desert Storm.
POUCH AND HEATER CONSTRUCTION
The big breakthrough was the pouch. Its three special layers allow the food to be sealed and then cooked (opposite from other food processing methods) and never exposed to the air again until opened. The food is actually sterilized in the pouch and then blocked from future contamination. The result is an excellent shelf life and food which retains its natural moisture and juice (i.e. it is not freeze dried or dehydrated). Here is the breakdown of the breakthrough pouch:
OUTER LAYER: A tough polyester film which provides protection for the middle layer and is an excellent printing surface.
MIDDLE LAYER: The key to the pouch's shelf stability is aluminum foil, the most effective and economical barrier to moisture, light and oxygen. The result: No refrigeration or freezing will ever be required.
INNER LAYER: Next to the food product is a very special polypropylene film. It Is compatible with the widest variety of foods so that no "canned" or other unwanted taste is added to the food. It also ensures an exceptionally strong heat seal.
There are water activated heaters designed to warm up MREs prior to consumption. Here's a little more detail on their composition and functionality. From MIL-R-44398 (Flameless Ration Heater):
DESIGN OF HEATER PAD. The heater pad consists of a supercorroding Mg-Fe alloy powder and an electrolyte together with flow and wetting agents dispersed throughout a porous matrix formed from polymeric powders. The magnesium and iron function as anode and cathode, respectively. The electrolyte is activated by the addition of water which initiates a rapid corrosion of the magnesium particles within the matrix. The products of the chemical reaction are heat, magnesium hydroxide, and gaseous hydrogen.
SHELF LIFE AND STORAGE/TEMPERATURE
A main concern in the development and testing of rations for our armed forces has always been shelf life. An amazing amount of research has been done in the development of the retort pouch and the MRE to determine the exact length of time and the exact conditions under which it is safe to store the entrees and side dishes. The main thing we have to work with is the shelf life chart (shown below) compiled by the Army's Natick Research labs. This gives a very good overview and summary of all the findings gathered from all the testing of MRE products. However, it leaves many questions unanswered. Here are additional facts and observations that have been gathered about MRE shelf life:
1) The shelf life ratings shown in the chart below were determined by taste panels, panels of "average" people, mostly office personnel at the Natick labs. Their opinions were combined to determine when a particular component or, in this case, the entire MRE ration, was no longer acceptable.
2) The shelf life determinations were made solely on the basis of taste, as it was discovered that acceptable nutritional content and basic product safety would extend way beyond the point where taste degradation would occur. This means that the MRE would be safe and give a high degree of food value long after the official expiration of the products as determined by taste.
3) MRE pouches have been tested and redesigned where necessary according to standards much more strict than for commercial food. They must be able to stand up to abuse tests such as obstacle course traversals in field clothing pockets, storage outdoors anywhere in the world, shipping under extremely rough circumstances (such as by half track over rocky terrain), 100% survival of parachute drops, 75% survival of free-fall air drops, severe repetitive vibration (1 hour at 1 G vibration), 7,920 individual pouch drops from 20 inches, and individual pouches being subjected to a static load of 200 lbs for 3 minutes.
4) Freezing an MRE retort pouch does not destroy the food inside, but repeated freezing increases the chances that the stretching and stressing of the pouch will cause a break in a layer of the laminated pouch. These pouches are made to withstand 1,000 flexes, but repetitive freezing does increase the failure rate by a small fraction of a percent.
Projections are that the 130 months will be surpassed. This chart contains storage life projections for MRE rations from the U.S. Army's Natick Research Laboratories and does not reflect a manufacturer's or vendor's guarantee.
NOTE: Time and temperature have a cumulative effect. For example, storage at 100oF (38oC) degrees for 11 months moved to 70oF (21oC) would lose one half of the 70oF (21oC) storage. *Wornick's, a retailer of MREs, puts their shelf life at less than the Army's findings. While the Army finds MREs acceptable for over 10-1/2 years stored at 60oF (16oC) , Wornick's places their shelf life for the same temperature at 7 years. I would tend to regard the lower time frame as accurate for several reasons:
1. The Army's findings for shelf life were based on "taste tests" of their Natick's Research Laboratories, not nutritional findings. 2. And this is certainly not scientific, but the military has traditionally been known for putting food in their troops bellies - period, not that it was particularly tasty or nutritious.
The above chart references sustained temperatures. MREs are not usually stored in controlled air-conditioned facilities for long periods of time. The product nutritional value and shelf-life may be compromised if an average temperature is not maintained. MREs should not be stored at temperatures around 25 - 30oF ( -3.8 to -1oC) because of possible reduction in quality. Rough handling of a frozen package can result in broken seals and fool spoilage. Frozen storage is not recommended.**
**However, this statement is in opposition to the US Army's statement: " MREs are designed to withstand harsh military transportation requirements, including airdrop with and without parachutes and storage at -60 degrees fahrenheit up to 120 degrees fahrenheit. (See MREs Fast FAQ for further information.)
Each MRE product is date coded with a series of numbers. The numbers include the production year, and the day produced in addition to a lot number extension. Look for a number stamped on the package that looks like 7055A B02A. Look at the first digit of the number 7055. The "7" stand for the last digit of the year, 1997. If you are buying from a disreputable dealer, it could also stand for 1986. Ask your dealer for clarification. The following three numbers "055" represents the 55th day of the year, or February 25th. The full breakdown of the date code would be February 25, 1997. The "B02A" is the lot number which can be ignored.
If no date or date code appears for a product and the company where the purchase was made sells only fresh and current MREs, mark each meal with the date of purchase OR mark the meal 7 years into the future. Whichever method you use, make sure you stick to the same one throughout your stored food purchases. This applies to canned good, medicines, dried foods, everything. If stored at the proper temperature, you'll have approximately 7 years' shelf life from date of purchase. If the company where you purchase MREs sells product made 2 years prior, note that date on your box and subtract two years from your pencilled-in expiration date. Example: If it is June 20, 1998 and the MRE source sells products 2 years old (which usually means they'll give you a better price), date your box with a permanent marker "Expire June 20, 2005".
Q) Is it true that MREs are laced with Saltpetre and will make me impotent?
A) This is a silly urban myth and should not be perpetuated. If you have any question of this, I will pass your address on to my girlfriend who will attest to the fact that on weekends of MRE meals my habits (wink wink nudge nudge) are not altered in the least. On the other hand MRE meals are chock full of Alum and eating too many will make your head shrink just like in the classic Warner Brothers cartoons.
Q) Will MRE meals constipate me?
A) It depends. MREs are low in moisture content. They do not constipate me, but different folks respond differently. If you maintain your normal fluid intake while consuming MREs you should have no problems. Some folks add water to their regular MRE entres to stretch them a bit and add more moisture.
DIETARY CONSIDERATIONS/NUTRITION CHART
Approximate Nutritional Values ( based on the average of 6 menus) Net Weight:493g Protein:25g Fat:32g Carbohydrates:149g Calories:933
*MREs are within MRDA (Military Recommended Dietary Allowances) guidelines for sodium content. One MRE (less the salt packet) provides approximately 1800 milligrams (mg) of sodium. The usual sodium intake of soldiers in garrison is 3000-6000 mg per day. Therefore, MREs are not much higher in sodium than typical garrison intakes. This sodium content is much too high for the average person. The military probably takes into account their personnel are much more active than the average civilian and would "sweat out" more salt. Also, 30% fat content is at the high end for acceptable dietary content and 40% is definitely too much fat in the diet. However, if one is active and burns off a lot of calories, this is acceptable for short term, emergency rations. Making a steady diet of this amount of fat is not clever.
Calculations of fiber content in rations indicate that relatively good sources of fiber include: pouch bread, fruits, peanut butter, potatoes augratin, stews, rice-containing entrees, nut cakes, cookies, and brownies. The fiber content of field rations, while not high, is adequate to prevent constipation. Insuring an adequate fluid intake is of greater importance in the prevention of constipation than the total fiber intake.
How to Heat MREs.
U. S. soldiers and thousands of Emergency Relief workers aroundthe world have been forced to eat MREs cold. They weren't intended to beeaten cold exactly, but one of their great advantages is that they canbe. MREs have served their purpose well with no reheating in personal emergencies,family emergencies, and city or state emergencies (earthquakes, toxic spills,hurricanes, tornadoes, blizzards, floods,etc.).
In most situations, however, there is time and opportunity to heat thisfood. Here are the best ways:
1) Boiling for 3-5 min. - take the pouch from outer cartonand place it in clean boiling water heated from available sources: fire,heating tabs, or stoves. 2) Placing next to a non-liquid heat source: radiator, engine block,or even the human body. Be careful of burning or melting the pouch if theheat source is too hot.
3) Placing in a chemical, non-flame heater. There are a couple kinds of civilian market heaters for retort pouches. One of these, Zestotherm, has even been adapted to Olive Drab format for military use and officially called the "MRE Heater". We sell these in bundles of 12 and also sell a version of our MRE Full Meals which includes an MRE Heater Pouch in each meal.
4) Microwave 2-3 min. after removing from the pouch. The pouch containsan aluminum, non-microwaveable layer which gives the pouch such a longshelf life.
Above information posted from the website safetycentral.com