Everything you ever wanted to know about storing emergency food in Alaska, version 2
I went back and did a lot more research on the article, the earlier comments regarding reservations using drywall were very good points.
So here it is again, version 2
BTW, Alaska Magazine rejected it - too long.
Everything you ever wanted to know about dry food storage, especially for cold climates.
I’ve been doing a good bit of research over the last 4 months about storing dry food for my “just in case” cache. I needed to be absolutely sure since my family’s life will be at stake if we ever need it. I’m very glad I did too; otherwise I would have destroyed most of my cache if I’d simply followed what I’d found with a cursory Google search. Storing outside in a shed in Alaska (or other cold climates) is different.
Alaska is particularly vulnerable to interruptions in food delivery from the lower 48, we’re remote and prone to earthquakes, tsunamis, volcanoes, and severe winter storms. Not to mention potential civil disruptions keeping the supply ships from being loaded in the first place.
Almost all of our food delivery goes through just a few fragile sea ports, mainly Anchorage. In a earthquake bad enough to damage the ports - the airport runways will be probably damaged too, so air freight is not really an option either, and in any case the sheer food tonnage required couldn’t be done.
FEMA and the American Red Cross recommend a minimum of 72 hours of food, water, and medicine on hand per person in a transportable format, this is sometimes called a “bug-out bag”. They further recommend having 2 weeks of supplies per person on hand at home for longer term emergencies. The state of Alaska recommends a 7 day “bug-out-bag”. Other government sources (post-Katrina) recommend 30 days home storage per person.
Personally, my family and I have about 3 months on hand and a 7 day bug-out bag.
This guide is also applicable for food storage in remote cabins or people who live way out in the bush and commonly buy large amounts of bulk foods “in town” only once or twice a year.
Food needs to be stored dry in an air & moisture tight container in a dark cool environment. The container also needs to be rodent proof. The most important factors are; storage temperature, oxygen, food water content, storage container humidity, and finally light – in about that order.
Absorbers: There are two routes you can go: buy premade desiccants and oxy absorbers online (or locally if you’re lucky) which will make the FDA happy or use field-expedient means which I’m certain the FDA has never evaluated but are still perfectly safe. I’ll talk about both means, premades are easier but if you’re in a situation where they’re not available I’ll talk you through the safe alternatives too.
Containers: Regular plastic sacks or food grade HDPE 5/6 gallon buckets are only good for short-term storage (<2-3 years) as oxygen and moisture will seep through the plastic and lid seals.
Your best bang for your buck is O2 blocking aluminized food grade mylar bags of at least 5 mil thickness, (7+ mils is recommended). These look like big thick versions of the silver anti-static bags that computer parts come in. Get the ones that need to be heat sealed (you can do it with a clothes iron) ziplock versions don’t seal perfectly.
These bags are not rodent/puncture proof by any means so they’ll need to be protected by placing them inside another container. 5/6 gallon plastic buckets are ideal but rubbermaid type containers will do in a pinch.
#10 (1 gallon) cans are best but they’re relatively expensive vs volume and you need specialized equipment to seal them.
Large glass canning jars could be an alternative, but they’re fragile and transparent (bad), plus you’d need to make sure the rubber seals would stay good for 10+ years. Personally, I wouldn’t use them.
Metal paint cans might also work, but they’ll need to have a enamel lining and your food should be double protected from touching the metal by being inside a plastic bag. I don’t know how well these would seal either. I’ve never heard of anybody using metal paint cans.
Temperature: For every 10.8 F below 70 degrees the storage life is doubled:
Temp F Years
37.6 ---- 40
48.4 ---- 30
59.2 ---- 20
70.0 ---- 10
80.8 ---- 5
91.6 ---- 2.5
102.4 ---- 1.25
So, in this example something with a 10 year standard shelf life stored at 59.2 degrees will last 20 years, something with a 2 year shelf life will last 4 years, etc. Conversely, if stored above 70 they will go bad that much quicker.
Store your food as cool as possible but do not allow it to freeze unless you take strong measures to remove 97% of the container moisture, more on that later.
Oxygen: Air is about 21% oxygen and 78% nitrogen; the remaining 1% is other gasses. Food will oxidize all by itself in its container, eventually using up all the available oxygen – but by that time your food has gone bad (or rancid if it contains any oils/fats).
In addition bulk wheat/flour, rice, beans, etc will almost invariably have insects eggs in it, if not the insects themselves - they’ll eventually die when all the available oxygen has bound to the food but by then they’ll have damaged your food, and who wants to eat dead bugs and old bug poo!
Finally, make sure that you buy “washed” wheat/beans/rice/etc to cut down on the numbers of the little buggers to start with; it’ll also prevent dirt and other potential contaminants.
So, at packing time you need to remove as much of the O2 as you can, quickly. There are two techniques used in conjunction that give the best results:
Purge the container with dry ice (or nitrogen) at packing time. Carbon dioxide is heavier than air and will displace the oxy/nitro atmosphere as it sublimates and fills up the container from the bottom. 4 ounces is enough to displace all the air inside a 5 gallon bucket but we’re looking to purge the air from inside the nooks and crannies of your food and this requires a bit of a flow so we’ll be putting in 6 ounces. Wear gloves when handling the dry ice; you can easily freeze your skin.
Dry ice is most commonly available in 5 pound blocks only, it costs about 9 dollars, that’s enough for 13 buckets and it keeps for a couple days so have everything set up and ready to go before you buy it. Don’t try to store dry ice in the freezer; it sublimates at minus 109F so the freezer isn’t going to help you, you’re much better off with a small cooler. In addition, if you’re in a high humidity area keep it in an airtight container like a zip-lock bag to help prevent water frost from forming on it.
No matter what you do there’ll still be a little oxygen in the container and inside the food itself that’ll leach out over time so you’ll need to soak this up too. The easiest means to do that is to toss in a couple of middling sized hand warmers on top of your food inside the container at sealing time.
You can spend more and buy “oxygen absorbers” online, but hand warmers are cheap, readily available, have the same ingredients, are non-toxic, and have a LOT of capacity that will remain and continue to scavenge micro O2 leaks over the years. Hand warmers are manufactured to food grade standards; after all they’re intended to be against sweaty moist skin for hours.
Get the warmers that have their own water included. Don’t worry about them getting too warm, standard oxy absorbers also get warm and they don’t stay warm very long. If you’re feeling paranoid you can wrap the warmer in a paper towel.
When the bag is sealed after the purging and O2 absorbing you’ll see within a few days that the bag will collapse itself hard to the food. This is happening for two reasons: First, you’re binding oxygen to the iron in the hand warmer and lowering the gas pressure inside your bag. Secondly, the food inside the container is actually absorbing the carbon dioxide and is also lowering pressure inside your bag; this does not change the food in any way. Both of these effects result in pulling a partial vacuum in your bag, it also serves as a visual confirmation that you got a good seal.
Anything with fats or oils (including brown rice and nuts) is especially vulnerable to oxidation; oxygen removal is critical to long term storage and I recommend that you put in twice the amount of absorbers as normal.
Water content. Dried bulk food such as beans/unground wheat/rice/pasta/etc has about 10% water content and are fairly bulletproof. They can be safely stored for 20+ years with just a standard desiccant package and oxy absorber inside the container to control relative humidity (RH) and storage in somewhat cool (but not freezing) conditions.
Powdered whole milk, powdered whole eggs, peanut butter powder, flours, and bisquick, are “delicate” and do not normally last longer than 5-8 years in storage and need special attention for O2 removal and must be DRY to achieve a 20+ year useable storage life when stored at 60 degrees or less. For these we’ll need to get container humidity down below 5%.
Desiccants; There are really only two types that you easily can find locally for field expedient use: The first is Silica Gel, which you can get at Wal-Mart or craft stores in their flower area, its used to dry flowers.
The other is dehydrated gypsum (aka Calcium Sulphate anhydride), which can be made from Plaster of Paris or garden gypsum. Gypsum is also in drywall but drywall has additives in it that I’d rather not deal with. You can still use drywall safely if heat treated properly and prevented from direct food contact (wrapped in a paper towel) but the other sources are consistently more pure, safer, and easier to deal with.
Silica gel can pull container relative humidity levels down to about 50% @ 60 degrees, it can absorb up to 40% of its weight in water at 70-95 degrees but mostly stops working by 35 degrees.
However, at lower temperatures & humidity levels it will release water vapor back into your container. (Bad Thing) It’s great if your food store is in the tropics but not so good for Alaska or any other area where cold temperatures are encountered.
I strongly advise against using silica gel unless you live in Florida, and even then you should use a clay-based desiccant.
I exclusively recommend dehydrated gypsum as it meets our needs best, if you don’t want to use field-expedient means to make it you can buy it online from a company called Drierite that produces food grade granulated dehydrated gypsum, you’ll still need to bundle it up though.
If you absolutely don’t want to bundle your own absorbers, buy clay-based desiccant packages, they perform about the same as silica gel at the same temperature ranges and at least they don’t release moisture back into your food but they also stop working when cold. If you’re completely sure your food store will NEVER get below 50 degrees a clay-based desiccant will meet your needs, otherwise go with gypsum.
You’ll need to understand relative humidity; it’s a function of water vapor saturation and temperature; as air cools down it can hold less water, the point when the cooling air starts condensing water is known as the “dew point” and that’s when we get dew or frost or fog. At a given temperature relative humidity is the percentage of water vapor in the air vs the maximum amount of vapor saturation before it starts condensing.
Dehydrated gypsum only absorbs about 7% of its weight in water; however it works down to a dewpoint of minus 100 degrees and is completely non-toxic and is cheap. It works by chemically binding water to its structure, it will not release water unless its heated above 360 degrees. It’s an ideal desiccant for food storage & very effective at what we want it to do, we just need to use a lot more.
The other common types are calcium oxide (quicklime), and molecular sieves. Quicklime is caustic & absorbs CO2, and moly sieves are expensive.
So, lets get to making our own dehydrated gypsum; “Plaster of Paris” in the red box is the most consistent chemically pure source of gypsum, it’s 70% gypsum and 30% hydrated lime – you could eat the stuff right out of the box (but I don’t think you’d enjoy it much). Fred Myers or any home center will have it. The second best source is garden gypsum but you have to be careful with that as some of it is made from recycled drywall (you can tell by opening the bag and seeing if there’re little bits of paper in it). For example Lowes “Greenacres” brand is made from recycled drywall, but their other brands are mined-from-the-ground gypsum.
Washington State has a great online database of agricultural soil amendments that gives us a chemical breakdown of fertilizer contents. Its found at: http://agr.wa.gov/PestFert/Fertilizers/ProductDatabase.aspx
Regardless of the source of your gypsum the heat treatment shown below will drive off any dangerous chemicals that can migrate to your food.
Safety Note: There was bad drywall imported into the US from China in 2003-2007, mainly in the Southeast US. It’s very unlikely we’ll encounter it, but we need to make sure our gypsum hasn’t been contaminated if you’re using a drywall-based gypsum source. Before you start baking, take a tablespoonful and get it slightly damp, then heat it up to about hot coffee temps (microwave works great) and give it a sniff. If it smells like rotten eggs then throw it all out and find another source – it’s contaminated and you can’t use it. It should smell kind of like a warm damp rock.
Spread the gypsum in a pan (1/2” layer max) and heat it up in the oven to 440 degrees for 5 hours, we can’t go any lower than 430 degrees or we won’t drive off any undesirables in our desiccant.
Make SURE you don’t go above 480 degrees or you’ll convert the gypsum to an anhydrous form that isn’t water soluble and is useless. Use a good oven thermometer to make sure, oven temp dials can be very unreliable. Don’t go above 440 degrees because the temperature swings in the oven when the burner is going can momentarily push it above the 480 degree mark.
After about 3 hours go ahead and stir your gypsum around a bit, you might see little wisps of steam – that’s a good thing. What we’re doing is driving off the water chemically bound to the gypsum and converting it to a form called γ-anhydrite and driving off other stuff the gypsum might have in it or absorbed from the environment. Stir again at 4 and 4 ¾ hours.
After we’re done heat treating our gypsum, we need to bundle our desiccant packages into balls: Pour one level ¾ cup in the middle of one strong paper towel (I used Viva) that’s in a bowl forming a partial pouch. After pouring gather up the sides and zip tie the mouth off, clip off the excess tie & paper towel. Then wrap another paper towel around it the opposite way and zip close that too so you have a double-layered ball. Don’t pack it too tightly - we want the powder to be somewhat loose.
The end result is a oblong ball about half the size of a tennis ball, you can also use double layers of large coffee filters.
Use white zip ties, we don’t want to use the black ones, they may contain a dye we don’t want in contact with our food. We don’t have to rush making our desiccant balls, but don’t take all day either, every minute they’re exposed to ambient air they’re soaking up moisture. They can be stored temporarily in gallon freezer bags as you’re making them, but afterward transfer them to an airtight container. Two of these desiccant balls should be good for a 5 gallon bucket. If you can wait for a day with a low humidity, you can tell if the humidity is low if you’re getting static zapped by doorknobs and the like.
Don’t use a rigid container like pill bottles for your desiccant units as they may break when the mylar bag crushes down from the vacuum the O2 removal & CO2 will cause.
Freezing conditions: This is why cold climates are different. If you are always going to keep your cache in 40-60 degree conditions, clay desiccants will work just fine. HOWEVER if it’ll EVER be exposed to freezing conditions you’ll need to use dehydrated gypsum.
Unless you have the interior of your container very dry AND are using a desiccant that keeps working in low temperatures. Freezing and near freezing conditions will allow water to condense as it gets colder and allow portions of your food to rise above 14% moisture content. Food at or above 14% moisture is in danger of allowing anaerobic (non oxygen using) salmonella bacteria to grow and produce the botulism toxin. Is it likely? Not really, but it’s not impossible for salmonella to grow at near freezing temperatures. In addition food can undergo a process called hydrolysis that will break down the nutritive value of your food.
Don’t try to use both silica gel and dehydrated gypsum as the gypsum can pull moisture out of the silica gel as the temperature gets lower which leads to elevated humidity levels in your cache.
Light: Light shining on your food, especially ultraviolet light from fluorescents or the sun will provide the energy to drive chemical reactions in your food, even in low O2 and moisture conditions, potentially degrading its nutritive value. Keep everything in opaque containers and/or in a dim area like a root cellar or basement.
Putting it all together: Now, finally, lets package our food. Line your buckets with your mylar bag, brush off any water frost from the dry ice surface and put 6 ounces in the bottom of your bucket, put a non-scented paper towel over it to help diffuse the CO2 gas, then fill bucket about half way.
Put two or more of your desiccant balls in and then pour the rest of your food in. Personally in my eggs, bisquick, and milk I put four desiccant balls in just to make sure. Make sure you’ve left yourself enough extra bag to close the mouth flat.
Now put the bag mouth flat on a 1” x 2” or so wooden board and heat seal the bag using a clothes iron on “wool” setting. Leave about 3 inches on one side unsealed, then close and fold that corner of your mylar bag shut with clothes pins or document binder clips, we don’t want an airtight seal just yet. Make sure you don’t iron in any wrinkles.
Let the dry ice sublimate and purge the bag, it can take up to 6 hours, I just let it go overnight since the CO2 is heavier than air and isn’t going anywhere. Don’t shake or disturb the bucket while purging – you’ll know its done sublimating when the bottom of the bucket is no longer cold.
After the dry ice is done sublimating open up the hand warmers and toss a couple in, try not to disturb the inside of the bag - we don’t want to mix our CO2 gas and ambient air. “Burp” the bag of the remaining gas then seal the rest of the mouth. You can also use foodsaver type sealers to do this too. Make SURE you don’t have any wrinkles, the wider the ironed seal the better. The iron will need to have a Teflon coating or it may stick to the mylar bag.
Mark the seal date on each container you package, you will also want to put the reconstitution directions and ratios for powdered items such as milk, eggs, instant coffee, etc on the outside of your containers. You probably won’t be able to remember exactly after a few years have gone by – I know I can’t.
Leave the bucket/bag in a relatively warm area (50-70 degrees) for a few days to give the desiccant a chance to remove most of the moisture, leave the bucket lid off so you can verify you got a good seal on your mylar bag. After a few days go ahead and store it wherever you want. I’d recommend you leave it in a 35 – 40 degree area for a week or two before exposing it to freezing temps. Don’t worry about the water in the hand warmer, the desiccant will pull the water out of it fairly quickly (which is why the hand warmer needs to work fast).
By the way, beans stored for a very long time or in very low humidity levels can become “hard seeds” which resist re-hydration by soaking in water. Scratch the seed/beans outer coat a little before soaking, or put the seeds/beans in a warm higher humidity environment for 3-4 days before cooking and they’ll rehydrate just fine. In addition, rice might have split in storage in low humidity conditions; it rehydrates and cooks fine with a couscous texture.
Salt, white sugar, honey, and Karo corn syrup have indefinite shelf lives right in the bag/bottle, the salt and sugar might turn into a solid brick requiring you to chip bits off and grind it up but it won’t go bad. Honey and Karo syrup may crystallize a bit in the bottle over time and/or if exposed to freezing temperatures, immersing the bottle in hot water will dissolve these crystals.
This article is primarily about how to store dry food, what to store is another multi-page article altogether!
Copyright reserved, presented here for personal use only.
Thanks. That was a lot of work. Interesting information.
Good one Maast! No comments this time! Let us know if it gets published.
Nice job putting together some important info.