Utilizing Oxygen Absorbers and Nitrogen Packing to Improve Emergency Food Storage

What more can be done to preserve food once it has been freeze dried?

The freeze drying procedure eliminates 98 percent of the water from food, eliminating insects and their eggs while also inhibiting bacterial development.

Beyond additional freeze drying to preserve food and extend shelf life, oxygen is the principal adversary. The shelf life of food can be extended by 25 to 30 years if it is not exposed to oxygen during storage. The term shelf life refers to the food's ability to retain its nutritional content, flavor, and appearance. It may still be safe to consume after this period, but the qualities listed above have been compromised.

Absorbers of Oxygen

To improve the shelf life of freeze-dried foods, some manufacturers utilize oxygen absorbers.

Oxygen absorbers are materials that chemically react with oxygen in their surroundings, combining with it and eliminating it from the environment. Iron, in the form of iron powder or iron carbonate, is the most often used material for absorbers. Both are quite effective when combined with oxygen.

Once exposed to oxygen, oxygen absorbers will continue to react with it until the material is entirely  oxidized, meaning it can no longer absorb oxygen. As a result, they must be properly packed and preserved to avoid being consumed before their intended use.

The oxygen absorbers are placed in the can of food before it is vacuum sealed, which is how they are utilized for freeze dried food preservation.

The theory is that any oxygen that escapes into the sealed container over time would be absorbed by it, rather than interacting with the freeze dried food and causing it to degrade.

There are two common types of oxygen absorbers. FreshPax from Multisorb Technologies is one kind. Type-B is utilized for wet foods like bread and processed meats, and it requires some moisture from the environment to operate. Type-D absorbers have their own moisture supply, making them ideal for dry goods such as freeze-dried meals. Any vacuum-packed container will be infiltrated by the surrounding air and, with it, the oxygen that makes up 21% of the air.

While the oxygen absorber will increase the shelf life by collecting oxygen in the air present during packing as well as air that seeps in over time, the absorber will ultimately be "maxed out," meaning it will be entirely oxidized and unable to absorb any more oxygen.

I've heard shelf life promises of 10-15 years for this style of packaged freeze dried food. 

This time period might be a reflection of the method and process controls used by the food manufacturer, as well as the oxygen absorber.

Nitrogen packaging

Nitrogen packing, often known as nitro-pak, uses a new technique to dealing with the "enemy" of oxygen.

Instead than relying on the container's qualities to combat intruding air, the container is flushed with nitrogen or packed in a nitrogen atmosphere. As a result, the sealed container has the same or slightly greater pressure than the open container, but it is filled with nitrogen rather than air. This indicates that air is not battling for entry. There is no such thing as abhorrence.

As a result, the period during which the food is not exposed to substantial levels of oxygen is significantly longer, and thus the possible shelf life is much greater.

When it comes to nitrogen-packed freeze-dried food, how long does it last?

On their website, Mountain House, the commercial brand of Oregon Freeze Dry, which has been active for over 40 years, says of their #10 freeze dried food cans:

"Our goods will have the longest shelf life...up to 30 years!" says the company.

It's possible that greater process controls, not only the nitrogen packing technique, are what allows them to make this remark.

There is information on the internet on how to nitro-pak foods with certain equipment, but I would be wary of believing your process control would be on par and your shelf life would be the same.

In any event, I've found that "nitro-pak" freeze dried food has the longest shelf life of any commercially available preserved food.