There are many methods one can use to preserve food, but one of the best, if not a bit tricky, is freeze drying. One advantage of freeze drying is that food preserved in this method can last longer than food preserved in virtually any other way. Freeze dried foods, if stored properly, can last for years, even decades, and taste exactly as they did the day they were bought fresh. The method has been around for some time now, but in more recent decades individuals have done it themselves in order to create rations for emergency and survival kits.
Because disasters are, by nature, usually a surprise to those they affect, it is important to store food that can last for a number of years in a bin, at room temperature, while remaining tasty and (more importantly) safe to eat. The variety of foods packed in most emergency kits are things like granola bars and canned goods, and have a limited variety. Freeze drying a number of foods is not only a way to add some variance to what you might have to eat for days or weeks on end in case of a catastrophe, but it can also provide a more varied, balanced diet; the ability to maintain normal nutrition and health in a crisis is important, though often underrated.
So, first things first, you’re going to need to get a hold of the following items:
Food to be freeze dried: Obviously, you’re going to need something to freeze dry. For your first attempts, I suggest fruits or vegetables. Try a technique with meat once you can freeze dry and re-thaw produce and have it not taste awful.
A metal tray
A freezer (it can be standalone or the one attached to your refrigerator).
A vacuum chamber (you likely don’t have this yet, hold off on purchasing this expensive piece of equipment until later on if you decide to freeze dry foods frequently.A vacuum sealer. Again, this is not necessary right away, but is preferable to trying to get the air out of Ziploc bags yourself when sealing for storage.
Preparation: Once you’ve got your food all lined up, cut it into small pieces – doing so will make sublimation (the essential process in which moisture leaves food to be freeze dried) much quicker. Also, make sure the food you’re using is fresh to start with, while flavor can be retained with practice, it won’t be improved by freeze drying, so make sure you start with something fresh. Finally, wash the food thoroughly.
Let’s start with the freezer method. For most people who have yet to purchase potentially prohibitively expensive equipment, this is the best method to start with. You will simply be using your own home freezer.
To start, take the sliced food from the preparation step and lay it out on a metal tray; the food should be evenly spaced and the pieces shouldn’t touch each other. Use a second tray if you have too much food prepared for the tray.
Next, place the food in the freezer. At this point, it is helpful to remove all other food from the freezer if possible (and place it in another one if you have it). Set the freezer’s temperature to the lowest (coldest) setting possible and open the freezer as seldom as possible, or not at all, while the food is freezing. All of these things will help the sublimation process quicken along. When using a professional freeze drying apparatus, pressure is used to bring the ice straight into a gaseous form, skipping over being a liquid. This isn’t going to happen in your freezer, but the quicker the water leaves the food the more successful you will be.
In a conventional freezer, this process will take about a week. After a week of freezing, remove a piece of food and let it thaw. If it turns black when thawed out (freezer burn), it’s not ready; toss out that piece of food, and leave the remaining pieces for a few days before repeating the test.
Once you can remove a piece of food without it turning to charcoal, you can move on to storing your food. Again, the easiest way to do with is with a vacuum sealer, but seeing as many people don’t have these, we’re going to use Ziploc bags and a little know-how. The idea here is to remove all air from the bag, so that moisture cannot form inside. Initially, you can use the standard “press-the-bag-all-over-and-try-to-squeeze-everything-out” method that you’ve probably been using on bags of potato chips since you were four years old. After this, however, we need to get that last bit out. The best way to do this is to use your mouth to suck the rest of the air out. A couple things: First, seal the Ziploc until there’s just enough space to fit your mouth, to form a vacuum. Second, your breath is moist, so the last thing you want to do is breathe out into the bag, for this reason make sure you start breathing in before your lips make contact with the bag. Once you’ve sucked the air out, quickly seal the bag; you’re done!
There are other, more expensive methods you can use, but this is by far the best one to start with. Before you get a freeze drying machine, you can take the in between step of using dry ice layers in a cooler to freeze things faster than a conventional freezer.
To rehydrate the food, simply boil water and pour it over the freeze dried food, it will return to, more or less, its original state.
Best of luck, and don’t be surprised if you need a few attempts before your food starts to taste like a proper meal!
Category: Food And Water