When I consult with preparedness planners about the various food options for long term storage, the foremost question is, “What is the shelf life?” Shelf life considerations for preparedness foods is an essential factor in effective preparedness and survival provisioning.
When I began in the natural foods/outdoor recreation/preparedness industry in the mid 70’s, shelf life concerns of dried food products was confined to the military, backpackers and the few folks who were preparing for the unforeseen and the impending tribulations. For the average person – who needs foods that will be palatable 10 – 20 – 30 years in the future? Packaging for longer shelf life dried foods was limited 40 years ago, and there were few companies at that time in the industry. Pouch foods for backpackers and campers had at best a few years shelf life. The companies that packed in #10 cans usually didn’t do anything effectively to ensure long shelf, which meant reducing residual oxygen levels. It was hit and miss depending on the specific food that was being canned. There were two exceptions that I knew of at the time – Arrowhead Mills in Texas and Oregon Freeze Dry in Oregon. Both companies would have the cans in a vacuum chamber and introduce nitrogen to displace oxygen. This is what my company at that time – AlpineAire Foods – did in the late 80’s with our can products called Gourmet Reserves.
In about 1990/91 things changed dramatically for effective shelf live packaging. I was introduced to Mitsubishi Gas Chemical America and their Ageless Oxygen Absorber. We had our cans and pouches tested by them and the results were extraordinary. Where military specs required a 2% residual oxygen level, the Ageless Absorber could reduce the levels to 0.1% or less! This significantly increased shelf life by reducing oxidation of foods. I was the first person in the industry to embrace this technology, and my company immediately began using these absorbers in our cans and pouches – and the rest is history. Currently it is an industry standard to use oxygen absorbers in foil pouches and #10 cans of dried foods. Companies that are still only using nitrogen flushing to reduce residual oxygen are utilizing an ineffective method and outdated technology.
WHY OXYGEN FREE?
Basically there are 2 reasons for wanting to store food in an oxygen free environment – (1) eliminate the possibility for infestation and spoilage from insects and microorganisms, and (2) control oxidation, which leads to the rancidity of fats and oils, foul taste, off color, and nutritional deterioration. The lower the oxygen levels – the more effective in preserving the integrity of the foods stored. Some foods are more susceptible to oxidation deterioration than others. It is important to know how susceptible the foods you are storing are to oxidation, because as you will see the type of container you store your foods in may at some point no longer be an adequate oxygen barrier. Research by Mitsubishi Gas Chemical Company, the inventors of oxygen absorbers and manufacturer of the Ageless® brand absorber, indicates that in an oxygen free atmosphere (their absorbers can reduce the residual oxygen level in the proper container to 0.1% or less) all adults, larvae, pupae, and eggs of the most prevalent dry food insects are killed within 14 days. Freezing a product – grains, beans, cereals, etc. – will not kill all microscopic eggs.
While oxidation has a distinct effect on most foods, there are some dried foods that are not as susceptible. Whole grains and beans being the most obvious, however there are some dried vegetables and processed cereals that seem to have an inherent long shelf life. That is why when opening containers of very old dried foods, some are spoiled and others may still be edible. The old adage still is applicable – If it looks OK, if it smells OK, and it tastes OK it is OK. Over long periods of time some nutritional value can be lost, however in an emergency situation you will have food to eat. It is still recommended that all long term storage foods be packed in a very low residual oxygen atmosphere.
I need to once again alert all those reading this article to be discerning, cautious and on your guard when buying so-called long term pouched emergency foods! I have written extensively about the deception and misinformation being delivered by businesses that call themselves emergency and/or survival food companies. I have over 40 years in the natural foods, emergency preparedness and outdoor recreation industries – I know deceitfulness when I see it.
The #1 red flag that indicates a deceptive claim and is used by the newer and untrustworthy companies is the fabricated 20 – 25 – 30 year shelf life claim of pouched foods in plastic buckets. It is interesting that some of these companies are now adding in small print the term “up to” on their packing and literature. I suppose if you stored your foods in Arctic conditions it might last that long, however most people do not store foods for 20-25-30 years in ideal conditions, and when you evaluate the packaging material and process, they are also less than adequate or ideal for these very extended shelf life claims. Also keep in mind that these companies are so new that there is NO anecdotal evidence of their misleading claims.
The material in which a dried food product is packed is essential in insuring an optimal shelf life.
Plastic buckets (HDPE – high density polyethylene) – 5 and 6 gallon round and square sizes with handles are very popular for packing grains, beans, and other commodities in bulk
- A convenient container to store larger quantities of dry foods – stores and stacks well, is compact, and can be carried easily.
- Inexpensive new and can be obtained used from a number of sources.
- A thick walled (90 mil) container with the proper gasket can be used effectively to control the atmosphere within for up to 2 to 4+ years.
- Can be used in conjunction with foil pouches for convenience of storage.
- You can use multiple foil pouches stored in the bucket for convenience of use.
- Insects don’t easily penetrate the thick walls.
- Can withstand some rough handling.
- Because insects at all stages are destroyed within about 14 days, the short term effectiveness of using an oxygen absorber to create an oxygen free environment is useful.
- HDPE is a permeable (porous – albeit microscopic) material and gas transmission rates (the length of time gases such as oxygen will travel through a given material) indicate that it will take 2 to 4 years for the atmosphere within the bucket to match the atmosphere outside (our normal atmosphere is normally about 21% oxygen and 79% nitrogen with a very small amount of other gases such as carbon dioxide). This means that if you started with an oxygen free or low level to begin with, that over time the oxygen level in the bucket will continue to increase until it reaches parity or equality with the normal atmosphere. Some foods will still be fine after the atmosphere has been equalized.
- If you want the atmosphere to remain constant inside your container, or be oxygen free for extended periods of time, HDPE plastic buckets are not appropriate – check with the manufacturers (as I have done) and find out their specifications and recommendations for your needs and the specific container you want to use.
- The ability to maintain whatever atmosphere you desire within the container will depend not only on the quality of the HDPE walls, but also the integrity of the gasket seal.
- HDPE will absorb odors and they will eventually permeate into the contents of the bucket. Direct packed foods will also absorb the odor. Do not store plastic buckets in areas that have a strong smell. (NOTE: Foil pouches within a bucket will prolong the odor absorption)
- Rodents and other animals can easily break into plastic buckets if left unattended for extended periods.
- Not recommended for long term storage (4+ years) of directly packed oxidation susceptible foods, although should be OK for whole grains and beans.
Pouches – There are literally hundreds of possible combinations of materials and sizes available to create a pouch that will contain food. Normally a food manufacturer or packer goes to a company that specializes in manufacturing pouches and gives the company their specifications and requirements for the specific foods to be packed.
IMPORTANT NOTE: It is common these days among those who sell empty pouches for food storage, or food already in pouches, to use the term “Mylar® pouch.” This is very misleading. By itself the term can mean anything and it tells you nothing of importance so that you can make the appropriate decisions on what pouch to use. The “Mylar®” brand is the registered trademark name of a PET polyester film manufactured by DuPont® Teijin Films. They produce hundreds of variations of this polyester resin material. It is a component used in the production of many variations of packaging material. It can be clear or opaque such as in wrappers for food bars or Mylar balloons – that look “metalized” yet contain no foil. Mylar® by itself is not an appropriate material for long term pouched food. Ask you supplier what they mean when they say “Mylar®.” A reliable pouch must have an appropriate layer of foil to be effective.
For those reading this article the requirements needed are to pack dry foods for the long term. If you buy stock pouches from a distributor you need to tell them what you plan to put in it and what your expectations are for the long term. You should insist on knowing the specifications (especially the gas and vapor transmission rates) of the pouch and whether they suit your needs.
If you want a pouch that gives you the longest possible shelf life for your foods, you will need a laminated pouch consisting of multiple components and layers. As far as pouches are concerned, one of those layers must be foil (NOTE: All plastics are gas and vapor permeable – some rates are very high – meaning that gases transmit through them very quickly – and some plastics both individually and in combination have slower rates). Only quality foil is a beneficial gas and moisture barrier – that is foil without microscopic holes). TRICK: Take an empty pouch into a dark room and put a small flashlight inside. No light should escape from the solid portion of the pouch. often you will see “pinholes” of light indicating a poor foil layer and/or rough handling, or significant light indicating no foil at all.
Ask the distributor the specifications of the pouch, the different components used – not only for barrier properties but also for durability, the transmission rates if not foil, if foil – its thickness, and the reliability and reputation of the manufacturer.
- The variety of available sizes offers flexibility in choices of quantities to store.
- Costs are reasonable.
- Can be effective as a short term oxygen free container.
- Small pouches of food can be very useful for bartering and distributing among those in need during in an emergency.
- Not recommended for very long term packaging of products for an oxygen free environment. Shelf life of pouched foods is recommended for 5 to 15 years depending on type of food product, storage conditions, handling, and composition packaging materials.
- Excessive or rough handling, loss of seal integrity, and pressure of sharp edges on the pouch from the products within can create “pin-holes” (microscopic holes in the pouch material) that eventually will cause gases to be transmitted through the pouch (NOTE: I am concerned when I see and hear some folks instructing people to cram and squeeze foil pouches into plastic buckets).
- Rodents and other creatures can easily penetrate pouch material.
Metal cans – For food storage purposes #10 size (about 7/8 gal) and #2 ½ size (about 7/8 qt) are the most popular used with the proper can sealers. It is possible, if you keep searching, to find 5 gallon square metal cans with a large pressure lid on the top side. These are ideal for bulk food storage, although they may be hard to find (NOTE: I sold these cans packed with foods at AlpineAire Foods about 20 years ago). You also may want to consider clean or new metal garbage cans as a means to store smaller size foil pouched foods.
- Ideal for long term food storage. The atmosphere within the cans, with the proper sealing, can remain oxygen free indefinitely.
- Metal is non-permeable for gas and water vapor – a zero transmission rate.
- Difficult for rodents or animals to penetrate.
- Can withstand some rough handling.
- Costs can be higher than other materials.
- Extra attention must be given to proper sealing.
- Metal containers may be difficult to obtain.
- Sealing equipment can be costly
- Some non enameled cans may rust if exposed to moisture.
- Excellent for long term food storage. The atmosphere within the jars, with the proper sealing, can remain oxygen free indefinitely.
- Glass is non-permeable for gas and water vapor – a zero transmission rate.
- Difficult for rodents or animals to penetrate.
- Easily obtainable and relatively inexpensive.
- Very fragile – must be stored and handled with care.
- Practical only in smaller size containers.
ABOUT GAS TRANSMISSION RATES FOR POUCHES
A gas transmission rate is the rate that atmospheric gases such as oxygen, nitrogen and water vapor will penetrate a pouch. Most pouches referred to as “mylar” have three layers known as PAL pouches. Plastic – usually a type of polyester film known as mylar®; Aluminum – a foil layer that should be at least .35 mil; Polyethylene – the material that seals the the pouch. All “mylar” pouches have transmission rates depending on the thickness and composition of the layers, and there are hundreds of different pouch sizes and compositions.
Basically a transmission rate is designated as the volume of gas (or weight in grams of water vapor) in cubic centimeters per a given area transmitted in a period of time. When looking at a typical good quality “mylar” pouch spec the O2 transmission rate is: 0.0006/cc/100 sq. in. in 24 hours. This means that 6 ten thousand’s of a cubic centimeter will transmit through a single side of a 10″ x 10″ pouch in one day. This is pouch material in an ideal condition and not the seams. While the transmission rates are slow in a quality pouch, over time the residual oxygen levels increase. Rough handling, poor seam sealing, puncturing from foods within and the side seams themselves can also cause additional “pin-holing” and leakage that will effect transmission rates.
Try this experiment yourself at home: Take an empty “mylar” pouch that is new or one from the pouched foods you are storing – have a small and powerful flashlight and insert it into the pouch – move it around the inner surface and seams. You will see light coming through at the seams, and depending on the thickness of the foil and pin-holing, you will see dots of light. These are the visible (there are still invisible and microscopic) areas in which gas transmission will occur.
The reason I have included this section in this article is to give some basis to appropriate shelf life claims. If shelf life is equated with very low residual oxygen levels – (and hopefully proper storage conditions) – then claims of a very long shelf life of pouched dried food products is compromised by ever increasing levels of oxygen over time within the pouch itself. Beware of long shelf life claims of pouched foods.
There are six conditions (plus Time) to be aware of when storing food for emergency preparedness food storage, or outdoor recreation. The foods being referred to in this post are shelf-stable freeze-dried, dehydrated, dried commodities. Optimal storage conditions can also be applied to wet pack: retort, MRE’s, canned goods, and other specialty longer term wet pack foods.
NOTE: The six conditions listed are chosen because these are factors in which we have the control to optimize for the longest reliable shelf life. TIME is the one factor that we can not control – and it does have a significant effect on the shelf life of various foods. Nutritional value is lost with many foods over time. To know with certainty the viable nutritional value of all food reserve items at any given time after a lengthy period of storage – is at best complex or most likely mere conjecture and guesswork. What we can do is to apply proper planning procedures – do your research with trusted resources, rotate and consume your storage foods, and be realistic about how long you will really need the foods you choose to store.
- Temperature– This is the primary factor affecting the storage life of foods. The cooler the better. 40 degrees-50 degrees would be great. Room temperature (65 degrees-72 degrees) or below is generally fine. Avoid above 90 degrees for extended periods of time. The longer food is exposed to very high temperatures the shorter the edible life and the faster the degeneration of nutritional value. Note: There are some “foods” available for emergency preparedness that are known as “emergency food or ration bars.” These products are generally referred to as “life raft bars” because they were originally designed for life rafts and can withstand high heat for extended periods of time. They primarily consist of white sugar and white flour, and were not meant to be the sole source of nutrition for a long period of time.
- Moisture– The lower the better. Moisture can deteriorate food value rapidly and create conditions that promote the growth of harmful organisms. The moisture level contained in foods varies depending on the type of product it is. Have foods in moisture barrier containers (metal, glass) in high humidity areas. NOTE: “Mylar” bags or plastic buckets are not a long term (over 3 years for buckets and 10 +/- years for bags) moisture or oxygen barrier. The moisture and gas transmission rates through these materials vary depending upon the specifications of the manufacturers. Plastic absorbs gases, moisture, and odors. NOTE: Be careful where you store dry foods in cans. Very cold flooring or any condition where there is a dramatic temperature differential may cause a build up of condensation inside the container.
- Oxygen – A high oxygen environment causes oxidation, which leads to discoloration, flavor loss, odors, rancidity and the breakdown of nutritional value in foods. It also allows insects to feed on dried food reserves. Without oxygen, insects cannot live, nor can aerobic (oxygen dependent) organisms. Whole grain and beans have natural oxygen barriers and can store for long periods of time in low humidity and if free from infestation. All other processed grains, vegetables, fruits, etc. must be in a very reduced (2% or less) oxygen environment for long term storage. NOTE: Mylar® bags or plastic buckets are not a long term moisture or oxygen barrier. The moisture and gas transmission rates through these materials vary depending upon the specifications of the manufacturers. Plastic absorbs gases, moisture, and odors. The best long term storage containers are glass and metal.
- Infestation – Examples include rodents, insects in all their stages of growth, mold, microorganisms, and any other creatures that get hungry – large or small. The proper packaging and storage conditions are required to control infestation and not allow critters to both get into the food, or have the necessary environment for them to flourish if they are sealed into a container – such as in the form of eggs or spores.
- Handling – Rough handling can not only damage the food itself, but it can also adversely effect and compromise the integrity of the container in which the food is stored. Glass of course can break; any pouched item can develop pin-holes, tears, or cracks. The seams on buckets and cans can be tweaked, twisted, or damaged to allow oxygen to enter the container.
- Light – Food should not be stored in direct sunlight. Both for the potential of high temperature, and its affect on food value. Sunlight directly on stored foods can destroy nutritional value and hasten the degeneration of food quality, taste, and appearance. Foods packed in light barrier containers do not pose a problem with the affects of light.