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Freeze dried food: a method within the reach of preppers?
L Joseph Mountain
This article has appeared by permission on Survivalblog and Freedomsphoenix.
Freeze dried food is all the rage among preppers for many good reasons. It’s hard to get the kind variety of prepared foods with with any other method. Rather than offering just ingredients, we can have all kids of entrees and tasty meals.
Properly freeze dried foods can exceed 30 years of shelf life, they are light weight and the foods retain more nutritional content than we see with other preservation techniques such as canning (often as low as 50% of original nutritional value) or dehydrating (usually around 80%). And unfortunately the nutrients at high risk are usually vitamins as opposed to proteins or starches. So freeze-drying is the method of choice where we want to preserve high vitamin content from fruits or vegetables.
This radical new method has been around since the 1940s and was originally developed as a way to get medicinal serums and medicines that required refrigeration to places which had no refrigeration. It was in fact yet another war-inspired technology until Clarence Birdseye started using it on food. Clarence’s big contribution was “flash-freezing” foods really quickly so water couldn’t freeze into large crystals but rather into tiny crystals on an almost molecular scale that didn’t physically destroy the food’s nutrition and texture.
Slow freezing doesn’t destroy things like vitamins by chemical change but by physical change: molecules are splintered, literally fractured apart is water crystallizes and suddenly expands while freezing. This is mostly what alters the texture of frozen foods. With dairy products we also see separation is water freezes out and leaves milk lipids sort of redistributed. Freezing cheese works fine but the unfrozen product will be crumbly, basically having been fractured up in freezing.
Some disagreement exists about nutritional quality loss with freeze drying, I’ve read more than once that it’s basically zero. I don’t accept this with other studies showing around 20% loss HOWEVER it seems in many of these tests the prep methods included heat, blanching or other processes that could easily account for nutrient loss.
The ability to flash freeze foods is one reason this method has been out of the reach of home preparers and it remains so. HOWEVER we are getting closer. Not only are some of the methods used to enhance more conventional home-prep methods now but we’re getting A LOT CLOSER to actual freeze drying at home. The level of DIY projects happening these days puts this technology much closer to prepper practice.
Let’s look at what freeze-drying is without getting too technical. First off it’s a process. The food is prepared, frozen, it’s dried once, it’s dried again and then packaged in a controlled environment.
The preparation phase isn’t a whole lot different from prep for canning or dehydration. We might chop the foods up, grind them, treat them with flavorings or stabilizers, whatever. It’s a really important phase because the food is rendered uniform and this gives more consistent quality at the end of the process. This is yet another edge that commercial food packagers have over us as they achieve higher levels of product consistency in prep.
Next, understand that pretty much everything that happens from here happens in absolutely sealed containers or environments.
The freezing phase is done the faster the better, and liquid nitrogen is really, really cold stuff. If it’s not that cold it turns into a gas. We’re talking around -60f (-50c to -80c) and this temperature is maintained constantly. Our household freezers don’t get that cold and they lose temperature rapidly by being opened and having a bunch of room temperature food crammed in.
Next is primary drying and this is done with warmer temps, depending on the food this might be around 0-10f with the food under low pressure, so a pump is busy pumping air out of the drying chamber and atmospheric pressure is dropping. What happens now is that the frozen water actually starts vaporizing and getting sucked out by the pump and there are vapor traps through the system to dispose of water which condenses back out into liquid at normal atmosphere and temp. And this is another thing that makes this method so desirable. All the spaces where water used to be is getting replaced with air or nitrogen gas. With normal dehydration those spaces are usually just getting filled up with food as it shrinks and condenses. With dehydration some foods are still fluffy. Dehydrated ice cream has to be the best example. Tastes like ice cream and has this aerated consistency. Fluffy is the only word I can think of to describe it.
This first drying phase of the process takes the food down to like 95% dehydration which pretty much blows away most of our conventional dehydration methods. Then there’s secondary drying which again is in a partial vacuum but the temps go higher to force out almost all remaining unfrozen water. This might be as high as 20f. At this point it’s hard to believe there is any water left but sometimes it’s chemically bound to the food and this breaks off even more.
Again the whole process here is under precise partial vacuum and at just the right temps, water will go from being a solid directly to being a gas. You skip the part where you have to heat up ice, melt it into water then boil it off into steam. This is called the “triple point”. As pressure and temperature decrease for a given food, there’s this triple point where ice “sublimates” right into a gas and it’s different from food to food and preparation to preparation. That’s another aspect that remains a challenge for home preparers because commercial outfits do very large batches of very similar foods, say the entire harvest of a peach orchard. They have the advantage of being able to run test batches, do some fine tuning and then just crank out repetitive batches one after another. Bigtime gain in efficiency. But as cheap electronic sensors become readily available we might make great strides and with our laptops even automate aspects of this process.
The final phase of this process is where the food is packaged and sealed, often in a dry nitrogen gas environment. Without that the food would at that point begin re-absorbing water, oxygen or whatever else is handy in the atmosphere. We really don’t want that, especially in the presence of any contaminants or chemical vapors. Naturally we pick impermeable packacking, air tight and water tight. Keep that in a cool, dark and dry environment and you have the longest shelf life of any food we can produce.
So that’s what it is. So now you understand how freeze drying works, the advantages and the technical challenges to us home preppers. This is not to say it can’t be done on the bench, we can get pretty cold coolants by using dry ice and alcohol slurries for “flash freezing” and due to millions of junk refrigerators & etc., cooling pumps and vacuum pumps are readily available. There’s DIYers experimenting with hybrid systems like this and taking regular freezers down to these temperature ranges. They seem to be achieving some partial freeze drying effects which I imagine will in fact produce storage benefits but it’s kinda trial-and-error. For handling fall apple harvest I really don’t want to be fooling around with hoses and buckets and slurry mixes, I wanna process, package and stow those apples all at once and as fast as I can.
What’s more enticing is watching the prices of commercial food freeze driers slowly come down into the $6k range and about half that for used ones. These are obviously smaller units, totally self-contained, about the size of a large floor model freezer. There’s the drying chamber, it’s pumps, a cooler and a condenser tank to keep sublimated water from freezing the pumps. There’s a bunch of controls and indicators to regulate things. And some of them have the freezer component built right into them. I saw one used on Alibaba for $3k, it was on wheels and it plugged into 220V power.
Now $3000 plus shipping for used equipment still isn’t what most of us think of as “home prepper economics” but to some of us or groups of us, this is getting closer.
Now this still doesn’t make flash freezing a practical reality for most of us and these units aren’t flash-freezers. However, besides the experimental methods above we have the possibility of buying flash frozen foods right off the shelf at the supermarket and freeze drying them. Plus, one thing I constantly learn, many of these practices can be partially implemented to improved effect. A freezer at 0f will freeze things a lot faster than one at 30f. With air moment and vacuum effect this is further improved. Ice crystals will be smaller, thence overall quality improved.
What happens if conventionally frozen foods are freeze dried? They get freeze dried is what. You get the light weight and enhanced storage longevity if packaged using our best home methods like nitrogen and mylar bags. This work-around allows us to skip intensive preparation of the foods that allow for uniform drying. So you basically get that we have the bits and pieces so to speak and ways we can kinda work into state of the art technologies.
This isn’t the fastest method in the world either. This whole process is stretching into days for any level or quantity of production so (for this level of equipment that is, I imagine the large producers are much faster). Plus we note that in the smaller units I discuss we don’t have that much rack space to stack food on. Maybe about 16′ square of rack space. This implies batches and holding food for processing and other hassles. All this and the associated power draw explains why these foods are so much more expensive in whole form let alone when we dry complicated entrees and meals.
As such I believe that freeze drying is around the corner for those of us who produce a lot of food or who cooperatively purchase and process it. You can keep track of equipment and prices on Ebay, on used restaruant equipment sites and regrettably, on Alibaba as most of this stuff is being made in China these days.
Earlier versions appear on Freedoms Phoenix Magazine and Survivalblog.
Many of the dehydrated “food storage units” available these days specify that you need a certain amount of fats or oils to supplement their unit. You probably know these units, they generally sell as “1 person, 1 year” type of packages and they contain a variety of grains, legumes, fruits other essentials. You might wonder why they don’t just include a container of oil to complete their units. Or even why we need them.
Fats are pretty chemically simple, carbon with oxygen and hydrogen attached. Not as complex as amino acids (proteins). This goes for saturated, unsaturated and polyunsaturated fats, the omega fats everybody loves to talk about these days, triglycerides and the cooking oil in your cupboard. Animal fats, vegetable fats are all this composition.
Fats (oils, lipids) are one of our bodies essential nutrients. While our bodies can manufacture some of the fat we need by using other nutrients, we can’t make enough of them. Fats are our body’s method of storing energy, lubricating joints and it turns out we need them to absorb a list of essential vitamins. They are not optional, we get sick and die without them. And in times of starvation our body burns off stored fat by converting it into energy (mostly by turning it into glucose which is the favored food of our cells.
Unfortunately the presence of these hydrogen and oxygen molecules aren’t all that stable and the hydrogen and oxygen tend to become attracted to and run off with the milk man so to speak. They can get together with each other and create water which will induce a milky or emuslified kind of appearing oil, and this would be a hydrolysis. I usually see this with oils that have been “annealed” or subject to repeated heating and cooling.
The other thing is they can combine with oxygen and we have oxidation. The latter is the issue we call “rancidity”. This is when you can smell it and you can taste it.
The major problem with rancidity is it first gives us unpleasant taste and odor and this progresses until the stuff is pretty much unpalatable. Oils and fats coat the inside of our mouths, making our taste buds more receptive to taste which is ordinarily great but if that taste is foul it’s foul with an electric guitar and amp.
There aren’t the kind of immediate health risks with rancid oils as there are from bacteria or other mean little bugs that grow on spoiled food however they can’t be able to do their job for us chemically as effectively as we need them to. This is that vitamin uptake thing. It’s also felt that rancid oils probably contribute to long term health issues like obesity. There might be some physiology where rancid oils burn less efficiently, and what the body can’t use or use as readily as carbs it might have a tendency to simply store. I’m not 100% certain on that.
However rancidity goes for all oils all the time, even oils in the foods we store up. Low fat beans store longer than high fat ones, white flour stores longer than whole wheat, white rice stores longer than whole grain or brown rice. Nuts go great in cans but nothing can stop the oils in them from rancififying over time. This is why cheap nuts often taste bitter. They are older stock.
The cooking oil on the supermarket shelf might have been in storage for months and this chemical change thing called rancidity has been happening this whole time. We can slow it down but we can’t stop it. The ways to slow it down are the very same general rules we use for all foods in long term storage:
1. Keep it cool.
2. Keep it out of sunlight.
3. Try to keep oxygen away from it.
4. Don’t let water adulterate it.
As well, it seems that the less refined-read SATURATED fats-seem to hold up best. Cold pressed extra virgin olive oil fits the bill but so does lard. Some of these cold pressed oils will hold up for months in proper storage and lard does great in cans (no light or oxygen penetration plus it’s free of acids and flavors found in other oils). And if it starts to taste a little harsh, well you just kind of deal with it until you get some more.
Perhaps most interesting to me is how fats operate in freeze dried scenarios and upon rehydration. The fats are pretty much still there even with the removal of all that hydrogen and oxygen and I have to remind myself that in fats these are chemically bound to carbon. It’s not water, it just contains the components thereof. I suspect there’s more going on there than I know at this time. Given as we can freeze dry meat, this is a real advantage for long term freeze dried storage. With normal dehydration these oils are basically unaltered and apparently more prone to spoilage.
If your diet is severely lacking in fats and you can’t find bacon, eat more whole grains. Eggs, milk, cheese all contain it. Corn is such a wonderful source of oil that if you grow enough you can press your own oil. The cautions come in if you are utterly dependent upon your stored food and have no hope of obtaining food (with fat in it) from outside sources. For me it’s hard to imagine this scenario but other preppers presume this level of isolation even for long periods. The RDA (gubment recommended daily allowance) of fat is about 60 grams so that’s about two avocados worth. Avocados are wonderful sources of dietary fat but again, most of the other foods you eat have fat as well.
L Joseph Mountain recently published Hidden Harvest, Long Term Food Storage Techniques For Rich And Poor. Available on Amazon, www.amazon.com/dp/B00BB7OZH0
Butter is quite easily and economically made at home, especially with a blender or food processer. Salted butter can be stored for weeks and even months at proper temperature. Canned butter can last as long as any other canned product. Butter has long been regarded by my people as an essential part of eggs and toast for breakfast. Butter is half of the justification for having refrigeration in the first place, the other half being to preserve medicines and serums for other arguably just as important life-saving activity.
So from the prepper or survivalist or self-sufficiency perspective, it looks like the butter-churn is coming back into fashion. Compared to other farm chores, it’s a welcome chance to sit down. It’s certainly more pleasant that actually obtaining the milk from the cow. Remember, with dairy processing, proper food handling and sanitation is really important. The critical phase of milk handling is the moment it comes out of the cow and into our environment. We need to cool it quickly and consume it or process it by any method here described. Raw milk can be strained and put into sanitized steel, glass or plastic containers for cooling, and can hang out in a proper root cellar for a week or longer. The cream will rise to the surface and can be used to richen certain things, used for butter or cheeses and the lower fat milk below consumed with your Wheaties. The nice thing about milk is we don’t have to wonder if it’s bad. Everything in us knows when we have a mouth full of bad milk, the nose knows it as soon as that milk comes close. Imagine being the man with the last box of Wheaties on planet Earth and you get to be the last man who can said you did when they say “better eat your Wheaties, men” and you had them with lowfat milk. You are gonna have a leg up on that day.
Curdling and cheesing is our way of making dairy product last longer. Cheesing can involve almost every art of food preservation previous to it and then some. Cheesing itself, curdling is ancient. In this we induce a change by chemical agents (usually acids or enzymes) in which the curds (solid product) get separated from the whey (liquid byproduct) in a process of rapid dehydration. The curds can be processed in any number of ways for long term storage. What most of us think of as cheese gets pressed and aged.
A cheesing site with lots of specific tips.
The levels of processing are hierarchical in terms of long term storage. At the shortest term is fresh. Curdling to remove H2O leaves a longer lasting product. Cheesing removes more H2O so it’s product lasts even longer, especially when salt is added. Aging cheeses can remove even more moisture and also allow for all kinds of GOOD fungi and bacteria which not only can flavor our cheeses but set up even more hostile environments for other micro-nasties we don’t want in our lives. Going one step further, we dip cheeses in hot wax for storage which puts a disinfected and air-tight layer around the cheese, even further inhibiting decay. Finally, cheeses can be canned, making a truly long term storable food. Canned cheese and butter can be bought from numerous suppliers. It’s amazing to thing the stuff starts as a liquid.
Storage terms or longevity of cheese is pretty much up in the air. Most of the cheese-making world considers maximum term to be about 10 years but French people would argue. For my cheeseworth, about 5 years produces some pretty sharp cheddar. There’s some older stuff that’s just sublime at parties but I wouldn’t eat it day to day. Cheese tends to harden and crumble over time as fats slowly sweat out. Younger, more elastic and milder cheeses are good for sandwiches.
Note that we assume these foods are packaged oxygen free for long term storage.
|Dehydrated||20+ years||Good||Good||Fair to good||Cheap||Yes||Yes|
|Freeze dried||20+ years||Great||Great||Fair to great||Pricey||Yes||No|
Just as packaged, dehydrated foods were the survival food of the 20th century, freeze dried foods are all the rage today. We get all the longevity, the light weight, the interesting recipes and we get better flavor and nutritional quality. We don’t get the compact form of dehydration and like dehydration, most dehydrated foods need rehydration which ups your water requirements, but it’s still great stuff for survival food.
Freeze drying is getting pretty high tech indeed. I think some guy called what’s-his-name invented it. Clarenece Birdseye. Anyways, remember how the crystallization of water in freezing tends to screw up the texture and nutritional content of food? Bird-man found a way that by rapidly freezing things really really cold–using stuff like liquid nitrogen–like colder than stuff normally gets on planet Earth, he managed to not only get around these problems but he found a way to extract tons of this frozen water out of the product when it heated back up to what we think of as normal freezing temperatures. With this technique we exceeded most previous preservation methods except the Pueblo dwellers who’s sprits still laugh at us and say “hope you liked the beans” which still happen to germinate. Unfortunately it’s a really high tech process involving highly specialized processing and equipment. We cannot freeze dry food at home.
Some argument exists as to the methods of freeze drying and whether some of them leave behind anything undesirable in our food. At this point there are many reputable vendors to choose from who pledge to sell us a quality product.
Preservation begins as soon as the organism is some kind of definition of “dead” which describes the cessation of respiration of an organism. It’s a rather imprecise definition as many cells of bodies and many cells hanging out on bodies continue to respire long after consciousness has left (Elvis has left the building) but we’ll leave such up to the mystics for now. What you need for dressing, gutting, skinning and butchering involves the following:
In brief your job here has 5 parts: cut, hang, bleed, gut, skin. So we start by cutting the animal deeply across the throat if that wasn’t their method of dispatch to begin with, severing the carotid arteries. The you hang the animal by it’s rear feet (or ankles more appropriately with a hook though their achilles tendons) and let the animal bleed out all it’s gonna. Catch the blood in a bucket for all kinds of uses if you want. I like to decapitate the animal at this point because it’s often easier to invert the animal following this point. You are ready to gut the animal.
Insert your long knife into the rectum and begin cutting around the abdomen and towards the rib cage, then right up (or down) through the middle of the rib cage and not stopping until you are through the chest and throat area. Whatever is inside of that body cavity comes out into a garbage can below. It can be lined in case you want to save the entrails for any number or purposes. And then you are ready to skin the animal. Watch for musk sacks on male animals. They will ruin your kill.
From there you can leave the carcass hang for days or even weeks in your root cellar and just age a bit. Meat’s fibers break down chemically as it ages and becomes more tender. And from there you can take it any way you want from leaving the carcass intact or going ahead and butchering and packaging the parts for freezing or drying or smoking or salting or what-have-you. Generally with a large animal you want to use all of the techniques as they each result in different flavors and have different resistances to composition. If one method fails you hopefully have meats preserved differently that made it.
With the above we’re kind of forced to know how to butcher. OK the guys in the supermarket with the white coats on, they don’t even know how to butcher anymore. It’s a real art but you don’t have to be the world’s greatest to reduce a full size animal into more manageable chunks. But I tend to take a lot of things for granted, and in this case, I can’t remember when I first dressed and butchered an animal. I don’t remember learning it. I think I probably saw it done so many times it was like picking up the phone was for us old people who remember phones when they were attached to walls. Nobody had to show us, when we got tall enough to pick the damn thing up is when the trouble started. Nowadays people have phones attached to their bodies. Now I’m not going to get too deep into butchery here. But in brief, if you have to, it’s cut, hang, bleed, gut, skin, dry.
Here is a really excellent paper on meat preservation. which is from a grassroots perspective. It includes a very basic butchering diagram.
A lot of microbiotics don’t like salty environment so begin with but salting has an effect similar to drying and smoking. Salt induces a peritonic response in the cells of meat. The cells of meat, alive or dead, still have cellular membranes that contain their moisture among other things. Salt puts them into a state of dehydration such that the cell walls harden and moisture tends not to come out and be available for the micronasty pool party. Now some will argue that this happens because of H2O exiting the cells by osmosis, but they are correct. Osmosis is one of those acey-deucey kind of phenomena: do minerals head AWAY from concentration or does H2O move TOWARDS dehydration? They both kinda happen at the same time. There is some factor of some micronasties just not being able to tolerate that saline an environment because it makes the H2O and minerals in their cells go crazy coping too, but the main effect or salt is this dehydrating (or hypermineralizing) effect.
Foods we traditionally salt are meats and seafood. The technique is rubbing salt (sea salt is good, we don’t use iodized salt) and spices if desired thickly into the meat on all sides. The resulting product can be dried, smoked or salt-packed which is placing pieces of salted meat into a container, packing meat and more salt in layers and so the meat isn’t touching the sides of the container and sealing it. The advantage here is the meat just keep desiccating and dehydrating over time. Since salt packing meat is a pretty manual process, a wide-mouth container is used. Metal and metal lids are not recommended for salt packing because of the corrosive nature of salt. Glass containers with wax or fat seals may be your reference. There are commercial curing agents in the supermarket for curing meat but I’ve never seen them used.
Brining is another salt reservation method for meat and fish. Brined meats are immersed and sealed into a saturated saline solution. This means the level of salt is at the point where no more can be dissolved in the solution. That’s over 3 pounds of salt per gallon of water. That’s a lotta salt. Again, we use non-iodized salt. Brining is used on raw or cooked meats and can last for many years. You can use your canning equipment for this method but as with salt packing we avoid metal containers and lids because of the corrosive nature of all that salt.
Jerking is a hybrid of smoking and drying salting meat. Salt your meat then smoke it and you have a much more durable food that can last years. It’s light, it’s ready to eat and it’s concentrated calories. It can be shredded and dropped into stew if you are sick to the point of tears of vegetable stew. Many people are only familiar with the strip-jerky found in stores today up on the counter, but some people still do jerk whole animals. Whole cows and horses and buffalo. This is traditionally done with the animal hanging in front of you. So the…ah…equipment is a bit different for a whole animal and there’s a lot more patience involved as we let nature do her work but it’s exactly the same besides that. For the most part, you want to stay more basic and make your cuts as even as you can, salting and smoking different cuts in batches. Moisture content for jerky is pretty much where you want it to be, but to be a durable long-term food you want it down below 15% in my estimation. Hanging your jerked meats in the root cellar is a find way of storing it.
Smoking happened when the sun first got serious competition in the heating industry. It’s doing the same thing as sun-drying or fire-drying but it’s not just the heat we’re after, it’s the smoke itself too. It’s faster than sun drying plus if you use the right woods it leaves a really appealing flavor particularly in meats, fish and cheeses. Cheeeeeeeeses. With the heat cranked up to about 120-140 °F, not a lot of micronasties can survive so the food actually approaches something close to the modern definition of sanitary.
Smoking dehydrates the outside layers of meat to form a kind of barrier on the outside so you don’t have to totally overcook things. The inside of meat is basically sterile until it’s in advanced decomposition and literally permeated by micro-nasties. With some woods like manzanita and pine, the pitch itself is a deterrent to microbials.
Nowadays they do all the commercial smoking of meats in smokehouses. In the old days, people used to just smoke meat in smokehouses. Often it was the same house known in other parts of the year as the “sugar shack”, which, contrary to contemporary belief, was not a house of lust and sin but rather a place where you boiled down maple sap to make syrup and maple sugar. It was typically a small structure which was designed to accommodate fire on the floor 24×7 and not burn down so the floors were generally stone. They were basically hearths, fireplaces that you stood inside of with the fire and the chimney was a hole in the roof. I’m really not thinking OSHA would approve of this working environment so just tell the building inspector it’s a children’s play house. The kids will agree, little animals that they are. There are few set global standards for how dry or what internal temperature should be achieved in smoking.
But before there were smoke houses there were much simpler and handier ways of smoking or drying and that’s a simple rack you fashion out of branches and saplings. You can tie them together with twine you make out of willow, hickory bark, the fibers from our Agave plants here in the desert or my favorite trick of running to the hardware store for a ball of twine. There’s no real official way to make a smoking rack, just get the meat over the heat.
People these days will tell you it just can’t or shouldn’t be done. Hooey. Dried and smoked meats can do very well in root cellars but humidity can be a problem there. In the case of larger pieces of meats, mold is allowed to grow on the outer surface, and cuts are taken deeper, and the freshly exposed meat surface just grows more mold. The interior of the meat, the meat on the inside is, I suspect, essentially sterile. I believe this is why we have such a long tradition transporting and storing meat as the whole carcass rather than vacu-packing final cuts for sale in supermarkets as we do today. Getting back to the focus, some meats can do well in dry shade, and “shade houses” used to be common in the Southwest. It’s a trick we picked up from the natives. These are above-ground structures that provide semi-shade. They work well in low-humidity environments. In general, if your smoked or dried meat starts rehydrating or even worse, moisture begins to condense on their surfaces, then you are starting to become concerned about too much moisture in that storage environment.