Building a dehydrator

[fishy1]

I'm planning to whip one up, pretty basic construction, just wood and 100w bulb and a few other pieces.

But I have some questions.

Why are dehydrators generally not very tall? They seem to be wide and not high. If I make mine a foot by a foot by 2ft high, I can fit in a lot, and as the stuff will all be pretty much above the bulb, on each tray it will all get dried equally. Of course, with this method, things on the bottom row will dry faster, but I can easily move rows around. Plus, with a tall design it will encourage much more air to be sucked in.

And another thing, why are things mostly dried on trays, sometimes with a few holes drilled in them? I would have thought the most effective way would be a screen. For now, I will just whip something up out of bamboo, but a stainless steel screen would also be a good idea. Now I think about it, it would be as good to put the material on kebab skewers and then it will not fall down holes as it shrinks. If my dehydrator is a success though, I might dredge up some old contacts from the pyrotechnics industry to see if I can get a fair bit of stainless steel mesh.

 

[Mike Ameling]

I am no "expert" on food dehydrators, but there are several things involved in their design and operation to consider and balance out.

Screen vs. Metal tray/plate with some holes: Screens work great, as long as what you are drying out won't fall through them - either before or during/after drying. But you also need to consider what material those screens are made from. Some are metal/wire, some are plastic, and some are metal wire that has a galvanized coating on it to retard rusting. The "food safety" of the material in your trays is important. And some foods "react" with certain metals when in contact. That's why a lot of commercially made food dehydrators have plastic trays.

The size and shape of the air holes through your tray material also affects how food will dry out. A "screen" looks fairly open, but it actually has a lot of metal blocking that air flow. Plus "slots" tend to allow better air flow than those "square holes" in screens. Fluid dynamics and flow prinicples are involved. Those engineers could tell you all the specifics on it. And what do you do if you want to make something like Fruit Leather? It's just dried pureed fruit, but that "mush" will run right through any screen or slotted tray. So you pour it on a cookey sheet with a lip around it. It does take longer to dry out than just the sliced fruit, but that "fruit jerky" sure tastes good.

You can build your dehydrator taller. But then you have to worry about that "heat" and "airflow" stuff. Taller actually also means LARGER overall. So you have more volume that needs to heat up, and also more area to lose heat through. And taller also means more trays or "baffles" to slow down and restrict the air flow. So you have to balance things out as to the amount of heat you add, and the size/location of your air intake/exhaust holes. Plus, you are trying to remove moisture in the food. But you also have to remove the moisture in the air itself going into your dehydrator.

Those "canned plans" for making a food dehydrator have already had all those "bugs" worked out of them, to reach a pretty optimum and balanced system. You can change things, but they you would be doing some of your own experimentation to find out what works best.

There are a number of good books on drying food out there, and most have a variety of tried-n-tested plans in them. You might try finding one to help you out. Mother Earth News magazine usually has a number for sale, as did Harrowsmith and Farmstead when they were still being published. And most natural food co-ops have a book selection on hand, and probably have a food drying book or two on hand.

Hope this helps.

Mikey - yee ol' grumpy German blacksmith out in the Hinterlands

 

[British Red]

100w light bulb will be fine, I'd include a cheap fan (say a computer fan) if you can to circulate the warmed air - it will improve efficiency no end. 2' high is big and I'd expect you will learn a lot in making the fist one and want to remake it. That said, you will lose 6" housing the bulb and fan so 2' sounds not too bad

Try cheap metal cooling trays for racks - they work well

Red

 

[Lush]

I used the oven to dry apple. It worked fantastic. The dried pieces taste wonderfull. It took 4,5 hours to dry two apples. I put the pieces into salt water for a few minutes first. Then I rinsed the pieces under the tap and dried them before putting them in the oven. First hour at 75 Celsius (167 F) , later on I switched to 50 Celsius (122 F). They came out perfectly light colored.

 

[fishy1]

Just curious, why did you put them in salt water? Do they taste salty? I was planning to use lemon juice and water.

I built my dehydrator, it seems to be working. The temperature on the top is about 25C, which is not much, but then the temp outside the dehydrator is about 10C. I reckon another bulb or two would be good.

I had some blaeberries I picked two days ago, they got a bit wet, when I opened the box thier was a lot of leaves and spiders, plus the smell of fermenting. This was not good, so I washed them and put in a pan, and I added 8 unripe cooking apples off my tree. I didn't bother peeling or coring them, I just quartered them. I then added a little water and simmered it all gently. Then, I had some redcurrants which I don't really like to eat fresh, so I added them as well, with a lot of thier stalks. I waited until the apples were soft and pulpy, then sieved it. I then added a bit of sugar, and spread it on trays. I then put it in the dehydrator, after 6 hours it is a little leathery but I'm leaving it for the morning to dry fully. It looks good.

 

[Lush]

The salt water is for making sure the apple are not going to get brown. Just like lemon juice. The apple does not taste salty. Vitamine C can also be used btw.

Vegetables have to be blanched before drying to preserve color and kill off enzymes...

 

[IntrepidStu]

Just curious, why did you put them in salt water? Do they taste salty? I was planning to use lemon juice and water.

I built my dehydrator, it seems to be working. The temperature on the top is about 25C, which is not much, but then the temp outside the dehydrator is about 10C. I reckon another bulb or two would be good.

I had some blaeberries I picked two days ago, they got a bit wet, when I opened the box thier was a lot of leaves and spiders, plus the smell of fermenting. This was not good, so I washed them and put in a pan, and I added 8 unripe cooking apples off my tree. I didn't bother peeling or coring them, I just quartered them. I then added a little water and simmered it all gently. Then, I had some redcurrants which I don't really like to eat fresh, so I added them as well, with a lot of thier stalks. I waited until the apples were soft and pulpy, then sieved it. I then added a bit of sugar, and spread it on trays. I then put it in the dehydrator, after 6 hours it is a little leathery but I'm leaving it for the morning to dry fully. It looks good.

Any chance of some plans ??
Cheers.
Stu.

 

[fishy1]

Maybe I'll get some plans, I'll certainly try and get some pictures.

I'm drying some carrots as well, they are nearly done. However, I didn't blanche them, will they just continue to decompose after drying because of this? They appear to still be orange apart from the ones I accidently dropped on the blaeberry tray which are now stained purple.

 

[rik_uk3]

Maybe I'll get some plans, I'll certainly try and get some pictures.

I'm drying some carrots as well, they are nearly done. However, I didn't blanche them, will they just continue to decompose after drying because of this? They appear to still be orange apart from the ones I accidently dropped on the blaeberry tray which are now stained purple.

I buy bulk packs of frozen veg, these are ready sliced and blanched plus often fresher than produce thats been sitting on a shelf a few days. They dry very well

Here is a 1 kilo pack (1 Kilo before drying) of sliced beans I dried, CD is to show size

http://www.alpharubicon.com/prepinfo/dehydratorstryder.htm Looks OK, but like most home made driers, they are big and bulky; my two driers are shop bought for about £25 each and can go in a kitchen cuboard when not needed

 

[Lush]

Maybe I'll get some plans, I'll certainly try and get some pictures.

I'm drying some carrots as well, they are nearly done. However, I didn't blanche them, will they just continue to decompose after drying because of this? They appear to still be orange apart from the ones I accidently dropped on the blaeberry tray which are now stained purple.

That I really don't know. Maybe it can be kept shorter.

Steam blanching is said to be best for preserving the most nutrients. I got most of my information from the National Center for Home Food Preservation.

 

[demographic]

I don't have the foggiest notion about them but am tagging onto the thread to see what info turns up, at least it will show up on mt subscriptions and not dissapear into the ether that way.

 

[fishy1]

Oh, anyone got any ideas for removing fruit leather from aluminium foil? Most of it peeled off but some remains.

And for next time, what should I use, clingfilm?

 

[British Red]

Silicon baking sheets are the best if you can lay your hands on some