The Shelf Life of Freeze Dried Food

Mountain House #10 Cans

There are four critical 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, then you must know these four factors in order to obtain 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.  The bottom line is that 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 many people will be able to achieve that.  Another factor is that you a place where the temperature is relatively constant.  Frequent temperature changes can also shorten the life of storable food.

In short, remember to store a cool, dry, dark place, where the temperature remains relatively constant. 

2) Moisture Content of the Food

Foods with excess moisture can spoil in their containers.  For long term storage, food should have a moisture content of 10% or less.  This can be hard to achieve because the average person doesn’t have specialized equipment. 

One option is to get freeze-dried foods, which are 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

Foods packed in air in storage containers will not store as well, as oxygen oxidizes many of the compounds in food.  Nitrogen is a popular gas for storing food.  It works very well.

Some people use oxygen absorber packets.  Just place one in the storage container and seal.  The one thing to remember is that the storage container must be able to withstand some vacuum pressure, as the absorber packet will create that as it absorbs the oxygen.

Most food units package food in nitrogen-packed #10 cans.

4) The Storage Container

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

One very important fact about storage containers is that they must be food grade containers.  #10 cans used for food storage often have an enamel lining.  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.  Make sure you purchase food-grade quality of buckets.  This is very important.

Remember these things when purchasing or creating a supply of stored food for your family.

Note – If you are specifically interested in the shelf life of Mountain House Freeze Dried Foods, please read this article:

Mountain House Freeze Dried Shelf Life and Packaging

How Freeze Dried Food is Made – Mountain House Freeze Dried Food

The Freeze Drying process

Freeze-drying has several advantages over other food preservation methods.  Freeze drying is actually a three step process.  It takes the three steps to freeze-dry the food, and a fourth step to reconstitute it just before it is eaten.

Let’s look at the advantages of freeze drying over other food preparation methods.  This will explain why freeze dried food is particularly well-suited for long term food storage programs.

Frozen foods retain fresh flavor and nutritional value, but require uniform, low temperature storage conditions, and that takes energy.  Dehydrated and canned foods are shelf-stable, but high-temperature processing can degrade flavor, texture and nutritional content. Freeze-drying combines the best of these processing methods. It preserves freshness, color and aroma similar to frozen food, while providing the shelf-stable convenience of canned and dehydrated food.

The freeze drying process of different foods varies with temperature, time, pressure, and other intermediate steps.  Foods are first tested for bacterial counts.  Next, the food may be cut into smaller pieces, depending on its original size.  For example, thick meats do not freeze dry very well, so they must be cut into smaller chunks before freeze drying.

Meat and seafood are then cooked before freeze drying.  Fruits and vegetables are washed first.  Some vegetables such as peas and corn have to be blanched.

The food is then placed on trays, the trays are placed in carts, and the carts are wheeled into cold rooms where the temperature can be as low as -40 F.  This causes the food to be frozen very quickly.

Next, the carts are moved from the cold room into the vacuum drying chamber.  The drying stage involves a process known as sublimation.  Sublimation is where a solid material is forced to change state into a gaseous state without ever becoming a liquid.  The process is started by removing the air with a vacuum pump.  The temperature is then raised to about 100 F.

Since the pressure in the chamber is below the point where water can simultaneously exist as a solid, liquid, and gaseous state (called the triple point), the heat causes the ice crystals to change into water vapor.  The vapor is then drawn off from the chamber, leaving only the food.

At this point, the dried food is filled with tiny voids, similar to a sponge.  These voids are where the ice crystals were once present.  This makes the food easier to absorb water when it is prepared for eating.

The dried food is then tested for moisture content and purity.  Some foods may be ground into small pieces or even into a powder.  Different ingredients are then blended together and the resulting food is packaged in airtight containers to prevent them from absorbing moisture from the air. 

Freeze-dried foods have several advantages over other types of food for long term storage.  They retain virtually all their fresh food taste and nutritional content.  They maintain their original shape and texture, unlike dehydrated foods which shrink and shrivel due to high temperature processing.  They weigh less than fresh food and take much less storage space.  Finally, they stay fresh and can be stored at room temperature in their original packaging.