Dehydration: The Basics

Sharon July 10th, 2008

You already know that there are a lot of ways to dehydrate, so now we’ll talk about the actual practice of drying stuff. 

Dehydration is probably the oldest food preservation strategy known to man, and almost certainly the most frequently used.  It isn’t difficult – the idea is that you remove enough of the water in foods to make them unattractive to bacteria.  Once you do so, the food should keep a long time.  Dehydration is one of the least energy intensive ways to store food, and while you can use electricity to do it, you don’t have to – so it is attractive from a sustainability perspective. 

Nutritionally, most dehydrated food is roughly equivalent (according to the Rodale Institute) to frozen food.  Most of the nutritional loss comes if you blanch things – the steam or boiling water takes a lot of nutrients.  Sometimes this is useful, though, because it preserves flavor, color and texture.  Because dried foods are concentrated, pound for pound they are much more nutritious than fresh foods.  They are also more nutritious than canned foods, which lose nutritional value through high heat.  That said, however, you do want to dehydrate at the lowest temperature possible and store it in a cool, dry, airtight place if you are concerned with nutrition.  Greens and herbs especially require care in that regard.  I usually dehydrate both of these by hanging in a cool, dark spot, rather than with any heat at all.

Generally speaking, you want your food to be quite dry – fruits (including tomatoes) can be 80% moisture free, because their acidity helps inhibit spoilage.  Low acid vegetables require 90% moisture removal.  In practice, this means that fruits can often be stored at the flexible, chewy stage, while most vegetables need to get to the crisp dry stage.

The bigger and thicker the piece of food, the longer it takes to dry.  Which means that generally speaking, you’ll want to cut things up.  Cherry tomatoes, green beans and smaller strawberries are about the only thing I dry whole.  Everything else gets sliced up. 

Blanching – this is one of those things that the experts vary on.  Blanching softens foods, and makes them hold color and texture better.  The best way to do it is to steam things a minute or two, rather than to put them in boiling water, which dissolves the nutrients.  My feeling is that blanching should be used only when it really improves the flavor of things, so while books like _Stocking Up_ recommend blanching grapes (?!?!), I think that’s totally nuts.  The only foods we blanch are tough skinned vegetables that seem to need it – green beans, sweet corn and zucchini.  The Rodale Institute also recommends blanching greens, but I dry them without it all the time – I’ve done both, and the color is definitely nicer if you do, but they work fine either way.  Really hard things like potatoes, carrots and pumpkin do need to be softened up a bit as well.  If you do blanch, do it for the minimum amount of time and plunge the food into cold water to stop the cooking immediately afterwards.

 Which brings me to the question of books.  The range of opinions on dehydrating is huge – someone in my class just reported that one book said that dried strawberries were bland.  We think they might be the food of actual divinities – and bland is not the word.  Some books recommend lots of blanching.  Some recommend almost none.  Some recommend microwave drying of herbs and greens – others say that the food gets cooked and the nutritional value destroyed (I think this latter opinion is actually right).  The truth is that you’ll probably have to experiment.  I actually think the most even-handed treatment of drying is in Carla Emery’s _The Encyclopedia of Country Living_ – which is newly released in the 10th edition (which I helped with recipe testing for before Carla’s death, btw).  She really offers a range of perspectives on pretreatments.  The only pre-treatment other than blanching I’ve ever used is asorbic acid – this means I crush a vitamin C tablet into some water and dip fruit into it, because it keeps the color.  If you don’t do it, it just won’t be quite as pretty.   I do this with apples and if I think about it, apricots.  The rest I don’t worry about.

The definitive book on the subject is _Dry It – You’ll Like It_ By Gen MacManiman.  It is a nice book, and not too expensive.  She also has a great website, with recipes and lots of information and her own line of dehydrators: http://www.dryit.com/ 

BTW, some people sulfur their fruit – I don’t, and I don’t recommend it – breathing sulfur isn’t good for you, it is just for pretty and the chemicals can cause severe allergic reactions in those sensitive to sulfites. 

 One traditional way to dry food is to hang it on thread – apples and green beans (leather britches) were the traditional foods done this way – the apples are cored and peeled and cut into rings, the green beans strung on a thread with a needle and hung up in an airy place to dry. 

So once you’ve decided what you want to dry, cut it into small, thin pieces, and lay it out in the dehydrator set up of your choice (if you want to use the sun, one way is to staple cheesecloth to light wooden frames and use tight strings across the back to support the weight of the food – don’t forget to cover the food with cheesecloth), and then check on it from time to time.  For most veggies, you’ll want it either crumbly or crisp, for fruits, you’ll want them quite stiff, and chewy.  If the fruits are sticky, you can toss them with something to seperate them – some cinnamon is nice. 

Once it is dry, if you are worried about insect eggs, you can freeze it for a couple of days or heat it up in your dehydrator or oven to 175 for 15 minutes. But usually just sticking it in an air-tight jar is enough.  But if you see any signs of condensation inside, your food is not dry enough, and should be dried more fast before it molds.  One option is after it dries to leave it out for a couple of days to further dry, stirring it every day.  Just keep an eye on it.  Then store it out in a cool, dark place in an airtight jar.  You can also determine if dry food is dry enough by weighing it – if you had a 10oz cup of strawberries before, the same number of berries should weigh 1-2 oz when appropriately dry. 

Dry foods keep a long time, but they do lose nutritional value in storage. Ideally you’ll eat most of them within 2 years, but greens and herbs should probably be used within one, at the longest.  

How to eat dried foods: We eat a lot of our straight – dried veggie chips, dried fruits, etc… are great eaten out of hand.  We also rehydrate them sometimes – fruit compote, where  a little water and wine is added and the dried fruit is stewed, or dried peppers or tomatoes are rehydrated in oil, adding a rich flavor.  If you are making soups or stews, just throw the dried vegetables in – greens at the last minute, but harder dry things like carrots and onions earlier.

We also use dried veggies as a flavorer – dry them to crispness, run through a blender or heavy-duty spice grinder and then add them as a seasoning.  The obvious choice here is onion or garlic powder, and can I just say how amazing homegrown garlic is powdered, compared to anything available at a store?  The same is true of home produced chili powder.  But you can get fancier than that – we use dehydrated tomatoes, onions and garlic together with some herbs to make a soup flavoring that can’t be beat.  Orange peel and dehydrated sweet peppers blended to powder are delicious together and brighten up just about any cooked dish. 

My kids love fruit leathers – just make a puree of fruit, a little lemon juice and sugar (if it needs it – if you use over-ripe fruit, you won’t), and those are great – you do need a special leather tray, though.  Don’t overlook the possibilities of chocolate-dipped dried fruits or other treats (lots on the Dry It! site linked above) as gifts!

Meats can be dehydrated, and store well after doing so.  Jerkies are one of those things you either like or don’t – we like them, but some people don’t.  The dryer you use for drying meats *MUST* be kept between 140 and 150 degrees at all times.  That means either very good care for solar dehydrating in a dehydrator system that gets HOT (but is kept low enough to avoid cooking), or an electric or wood dehydratore – period.  Don’t mess with it. 

Only beef from non-factory farmed, grass-fed sources, venison, moose and fish from safe waters should be dehydrated from a raw state.  All other meats must be completely cooked before drying.  The USDA recommends that all game meats should be frozen for at least 2 months before using, to kill all micro-organisms.  Also only extremely lean meats – less than 10% fat are recommended, since the fats turn rancid and ruin the taste of the jerky.   All jerky meats need to be marinated in a salty or soy saucy marinade before drying – the salt breaks down tissues, softens and kills insects and helps preserve the meat (we’ll talk about salting itself shortly). 

To 1lb of meat you need 1 1/2 cups salt dissolved in 1 gallon of water or 1/2 cup of soy sauce (soy taste better) – fish needs 1 cup of salt to the same quantity of water, and both should marinate for 24 hours.  Cut off every bit of fat or gristle, cut into thin strips and dehydrate until leathery and tough.  Store in a cool dark place for up to 2 months, checking for signs of rancidity, or freeze it for up to a year.    White fleshed fish and salmon dry best – oily fishes like mackerel or bluefish don’t do as well.

Ok, that covers most of the basics.

Also: I found this cool link online for a wood fired dehydrator for large scale projects: http://www.backwoodshome.com/articles/hooker41.html

Sharon

7 Responses to “Dehydration: The Basics”

  1. Cynthia says:

    Perhaps this is naive, but I wonder if a slow cooker set on low, with a rack ro something to keep the food off the bottom, could pinch hit as a dehydrator? I suppose the lid would need to be off, or maybe half off? I may try this, unless someone knows already that it won’t work. Anybody done this?

  2. Sharon says:

    I think slow cookers get to much too high a temperature, and there is no way of circulating air, so the heating would be uneven.

    Sharon

  3. Ginny in WI says:

    Ooh, DH is addicted to jerky, I bet he’d get into making his own!

    Are the plastic (non-sealing) caps that you can buy for canning jars airtight?

  4. emeeathome says:

    One of my best dehydrated flavourings happened the year we collected 200 litres of mushrooms. We lived up the bush with no electricity, so I dried them on sheets of galvanised iron and in the slow combustion oven with its door open. The 200 litres went down to 1 litre of powdered mushroom. A teaspoonful was delicious in soups and casseroles.

    I also did apricots the same way – the most successful apricots I have ever done.

  5. Sharon says:

    Ginny, I’m sorry – I don’t know if they are airtight. You might call the company that makes them and ask them – I’ve never used them.

    Sharon

  6. Hugh Dyment says:

    I live in rural Alaska where we preserve foods as a matter of course. My wife is Native Alaskan (Yupik Eskimo), and we live 400 miles west of the Anchorage-Fairbanks road system. In the past month we’ve preserved about 250 pounds of salmon. Most of this was dried and smoked in the same way my wife’s ancestors have done for millennia, and some was kept by packing in salt in 5 gallon buckets.
    Stumbling across your website was a pleasure. Preserving the land’s abundance has been, and is, a necessity in rural Alaska. I’ll follow the website and comment where apporpriate.

    Hugh

  7. Thanks and keep post such a informative blogs.

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