SciTech

How Things Work: Meals Ready to Eat

Before we get started, I?d like to take this opportunity to thank Bill Nicoll, our faithful How Things Work guy, for writing this column for the past year. Bill is off to Germany for a year of study abroad. He will be sorely missed. Bill is already sorely missed, mostly by me, who had to sub for him this week.

After Hurricane Katrina came and went, those left behind were stranded with nothing to eat. Those who had not stocked up on food probably came by their meals via an extremely tardy National Guardsman ? and that meal was in the form of a Meal Ready to Eat, or MRE. Because natural disasters can strike anywhere at any time, it behooves all of us to know our facts about this military manna wrapped in green plastic. Be prepared!

First of all, the MRE is not imperishable. Under the wrong conditions, it will shrivel up and die. According to the Army, the MRE can be maintained for three years at 80?F or six months at 100?F and remain ?highly acceptable.? At 108?F, it won?t last a month. A word to the wise: check that expiration date.

Since its introduction, the MRE has been the prepackaged Meal continually Rejected by Everyone. That is not to say the menu does not sound appetizing! Delicacies include ?Jambalaya? and ?Beef Patty and Nacho Cheese Pretzels.? Unfortunately, sometimes the titles leave too little to the imagination, like ?Chicken Breast Filet with Rib Meat Chunked and Formed, Breaded in Tomato Sauce with Cavatelli.? Chunked and formed? I?ll pass.

Besides the entree, the recipient gets a number of accessories, including a flameless heater, crackers, a small bottle of Tabasco, and a chocolate bar. Of course, the flameless heater is the most important part. Hot nasty food is always superior to cold nasty food.

In the past, soldiers would use a small piece of C4 to boil water for their meals. But nowadays, instead of plastic explosives, these modern heaters contain magnesium, iron dust, and some salt. When mixed with water, the ensuing oxidation reaction rapidly heats the water to its boiling point. To heat the meal, simply insert the heater and the MRE pouch back in the little cardboard box.

Rounding off the MRE is a special chocolate bar. During the Gulf War, American soldiers attempting to distribute imperialist chocolates soon learned that melted chocolate looks bad, even on camouflage uniforms. Thus it became a matter of national importance for food engineers to find a way to make chocolate bars that do not melt in desert heat. They used special emulsifiers that isolate fats in chocolate to prevent it from flowing. Even when melted, the separated fats cannot flow together to melt the bar.

Choco Sol President Victor Davila explains in the July/August 1997 issue of Professional Candy Buyer (yes, it?s real): ?If you take water and add sand to it, the water will become less flowable; however, it is still liquid. When applying the same principle to chocolate compositions, the fat in the chocolate, although still liquid at elevated temperatures, is now unable to become continuous. That is, it appears to be non-melting.?

MREs must be preserved for long periods of time. Food preservation revolves around eliminating the naturally occurring bacteria in the food. Some MREs use a lot of chemical preservatives, but there are other ways to give food a long shelf life.

Dehydration is the coolest method of preservation and involves some subtle thermodynamics. The food is placed inside a sealed metal chamber (think Time To Kill). The process begins with a refrigerator lowering the temperature inside the chamber. The food is frozen solid, isolating the water in the food on a molecular level from everything else. Next, a vacuum pump sucks air out of the chamber, lowering the pressure to below 0.06 atmospheres. The chamber is heated slightly, causing the ice to change phase directly into water vapor. This water vapor is then evacuated from the chamber. The process is repeated many times until the material dries out.

I ate an MRE once. I recall visiting the men?s room once every 20 minutes for several hours thereafter. So watch out during your next natural disaster, for internal disasters may also be coming! I would recommend a flavor or two, but unfortunately they?re all pretty horrific.