Survival Food – Freeze Dried & MRE

The Shelf Life of Long Term Food Storage Items

By Frank Salvo

There are four main factors that determine the shelf life of your long term food storage items. If you are looking to start a food storage program for your family, or you already have one, you will want to be aware of these things in order to get the maximum shelf life possible.

The four factors are as follows. The temperature of the storage area, the moisture content of the food, the atmosphere in the storage container, and the storage container itself. Let’s look at each of those factors.

1) Temperature of the Storage Area

Temperature has more to do with how long storable food will last than anything else. If you are planning on storing your food in a warm environment, it will only last a fraction of the time it would last in a cool, dry place. Some feel that the optimum temperature is 40 degrees F or less. However, not everyone will be able to achieve that. Another factor is that you have a place where the temperature is relatively constant. Frequent temperature changes can also shorten the life of storable food.

Remember to choose a cool, dry, dark place, where the temperature remains relatively constant, for storing your food.

2) Moisture Content of the Food

Foods with excess moisture can spoil in their containers. Food chosen for long term storage should have a moisture content of 10% or less. This is hard to achieve because most people don’t have access to specialized equipment.

An alternative is to get freeze-dried food, which has been specially-prepared for this purpose. The moisture content of these foods has been taken care of in the preparation process.

3) Atmosphere in the Storage Container

Oxygen oxidizes many of the compounds in food, so foods packed in air in storage containers will not store as well as Nitrogen, which is a popular gas for storing food, and one that works very well.

Some people use oxygen absorber packets. You simply place one in the storage container and seal. When you use these, you must have a storage container that is able to withstand some vacuum pressure. This is because the absorber packet will create a slight vacuum as it absorbs the oxygen.

Most food units that are packaged and sold for long term food storage have been packed with nitrogen in the #10 cans.

4) The Storage Container

Storage containers should have a hermetic seal (air tight) in order to get the longest life out of your stored foods. #10 Cans and sealable food-grade storage buckets work very well for this.

You must make certain that the storage containers you use are food grade containers. #10 cans that are used for food storage often have an enamel lining for this purpose. You can also buy plastic food-grade 5 gallon buckets.

If you buy a commercially-prepared food unit with #10 cans, then the second, third, and fourth factors are already addressed for you. In order to satisfy the first factor, you will still want to store the food in a cool, dry, dark place.

If you decide to buy plastic buckets, add the food, and seal them yourself, you will need to rent a nitrogen cylinder to fill the airspace in the buckets. When you do this, the oxygen will be displaced leaving only the nitrogen. Again, make sure that you purchase food-grade quality buckets. This is very important.

Remember these things when purchasing or creating a supply of long term storable food for your family.

Frank Salvo has been involved in food storage and emergency preparedness for the past 20 years. To learn more about these topics, please visit: http://www.freezedriedsurvivalfood.com.

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Utah State University has a classic food storage  advice document on it’s website.

The document titled “Food Storage in the Home” set the standard for food storage advice for years to come. Published by  Charlotte P. Brennand, PhD, and Deloy G. Hendricks, PhD of the Department of Nutrition & Food Sciences, “Food Storage in the Home”  focuses on “Reducing Waste and Maintaining the Quality of Stored Food”

They analyzed over 10,000 food storage systems in Utah in their research.

The concise 20 page pdf file covers what food to store, the storage area, and storage life.  A surprising observation I found in this document regarding how much food to store was;

If you were to sample most Utah family food storage programs in November, about 45 percent would have adequate stores of food for one year. If the same families were resampled in May only 20 percent would still have a years supply on hand. Families which did not have a years supply in May had used food from storage and had no garden or orchard to replenish the supply during the winter months.

They go on to recommend you have a long term food storage that has a peak 18 months supply if you are planning to always have a years supply. This makes sense if you are utilizing a garden approach to supplement your food supply.

What was even more shocking though was this finding on page six;

Families that were resampled and still had a years supply in May did so because they never used food from their storage system. We have analyzed over 10,000 food storage systems in Utah and found that many people are under the illusion that food lasts forever. Their food storage systems are designed so that a years supply is purchased and stored until needed. Consequently they have some stored food that is 10, 20, and 25 years old. In view of what is known about shelf-life, these systems are quite wasteful and inefficient.

Under this illusion what people thought they had, a years supply, disappeared when they went to use it.  Not a comforting thought. They had solved the problem by not drawing on their reserve but in the end they had no reserve, the food was inedible.

This would not be the case with freeze dried food however. Having freeze dried food that is 10, 20, and 25 years old in a food storage area means the food is still good and delicious to eat.

How many people who start something are able to follow thru and stick to the plan for months or years to come?

After food has been freeze dried what else can be done to preserve it?

The freeze drying process removes 98% of the water from food, stopping bacterial growth as well as killing insects and their eggs.

Beyond freeze drying further to preserve food and increase shelf life, oxygen is the main enemy. If the food is stored in a way that it is not exposed to oxygen, the shelf life can reach 25 to 30 years. Shelf life here refers to the food maintaining it’s properties of nutritional value, taste, and appearance. It may still be safe to eat beyond this time but the aforementioned properties are degraded.

Oxygen Absorbers

Some freeze dried food producers use oxygen absorbers to extend shelf life.

Oxygen absorbers are materials that chemically react with oxygen in the environment they are in, combining with the oxygen and thus removing it from that environment. The most commonly used material for absorbers is iron in the forms of iron powder or iron carbonate. Both combine with oxygen very effectively.

Once oxygen absorbers are exposed to oxygen they will continue to react with it until the material is fully “oxidized” meaning it can not absorb any more oxygen. For this reason they need to be very carefully sealed and stored so that they are not consumed before their intended use.

The application in which oxygen absorbers are used for freeze dried food storage is to place them in the can of food before it is vacuum sealed.

The idea is that any oxygen that leaks into the sealed container over years of storage will be absorbed by it, rather than the oxygen reacting with the freeze dried food and degrading it.

There are two types of oxygen absorbers commonly used. One type, Multisorb Technologies’ FreshPax Type-B requires some moisture from the environment it is in to be present to work and is used for moist foods like bread and processed meats. Type-D absorbers contain there own moisture source and are thus suited to dry foods like freeze dried food.

You may remember the old adage Aristotle proclaimed in 350 BC, “nature abhors a vacuum”. So any vacuum packed container will over time be invaded, if ever so slightly, by the surrounding air and with it the 21% of air that is oxygen.

So while the oxygen absorber will extend the shelf life by absorbing the oxygen in the air that is present initially during packing as well as the air that leaks in over time, eventually the absorber will be “maxed out”, that is it will be fully oxidized and can not absorb any more oxygen.

I have seen the guarantees for shelf life for this type packed freeze dried food at 10-15 years. This period may be a reflection of the limit of the process and process controls that the producer of the food uses, as well as that of the oxygen absorber.

Nitrogen Packing

Nitrogen packing or “nitro-pak” on the other hand takes a different approach to dealing with oxygen “enemy”.

Rather than relying on the properties of the container to fight the invading air trying to get in, the container is flushed with nitrogen or packed in a nitrogen environment. As a result the sealed container has the same or slightly higher pressure but with nitrogen and not air. This means that air is not fighting to get in. There is no abhorrence so to speak.

Thus the period that the food remains unexposed to significant concentrations of oxygen is much longer and thus the possible shelf life is longer.

What is the longest shelf life for nitrogen packed freeze dried food?

Mountain House, the commercial brand of Oregon Freeze Dry which has been around for over 40 years, states on their web site regarding their #10 cans of freeze dried food;

“Our foods will have the longest shelf life available…up to 30 years!”

It may be the result of superior process controls, not only the nitrogen packing process, that makes them feel comfortable making this statement.

There is information online on how you can nitro-pak foods yourself with some equipment but I would be leery of assuming your process control would be on the same par and have the same shelf life.

In any case “nitro-pak” freeze dried food has the longest shelf life for any type of commercially available stored food I have seen.

References on oxygen absorbers, nitrogen packing, and freeze dried food;

Wikipedia – Oxygen Absorber

Walton Feed – A Short Lesson on Oxygen Absorbers

Walton Feed – Storing Your Food Using Compressed Gas Such as Argon or Nitrogen

Nitro-Pak – Freeze Dried Food Reserves