Food Dehydrator

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Introduction: Food Dehydrator

I wanted to make some Jerky. Dehydrators run about €150 up over here, and I didn't want to tie the oven up for two days, so I decide to make one.

They're pretty simple, just a box with a rack, a fan, and a heating element.

Step 1: Ingredients

Repurposed storage box
AC 220v computer fan
Light on flex
Plug timer
Pliers / snips
Screwdriver
Coat Hangers to make rack
Knife
Tape
Glue, not pictured

Step 2: Wiring

Cut light flex, strip and expose wires.

The fan is a 220v AC fan, so can be wired straight to the plug.

I removed the bulldog clip at this stage.

Step 3: Wire It All Up

I attached fan+, socket+, and plug+ together, then covered the join in insulating tape. Then did the same with the other side.

Step 4: Test

Plug it in.

IT'S ALIVE !

Step 5: Making Some Holes

Marked two holes, one for the fan, one for the light, at the bottom end of the box.

Carved it out with a craft blade and a knife. The knife was more effective.

Step 6: Some Cracking

Got a little over eager, and pushed too hard, which led to some cracking and chipping.

The dog in the last picture was super critical.

Step 7: Mount Light and Fan

Light fixture screws apart, so pushed the bottom through and screwed the top back on to hold it in place.

Fan was mounted with glue. Tried superglue first, but it cracked off, so ended up using Tec 7.

Step 8: Take It for a Test Drive

Meat in, turn it on. I'm using a Peri Peri, balsamic vinegar, and himalayan pink salt rub.

Lid is left slightly ajar at the opposite end from the fan. I may make a vent if this doesn't work properly.

Made a rack from the coat hangers in the first picture.

Lined the bottom with tin foil to catch any drips.

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    42 Comments

    Mmm Botulism instructables style!

    Seriously, this is pretty unsafe. Better off using an oven. I believe you need a regulated 60°c to properly dry beef that is cut thin. The other issue is that type of plastic is toxic when heated.

    1 reply

    Botulism is not of concern here, because it is an anaerobic bacterium. However, I agree that this is pretty borderline in terms of food safety.

    Jerky (and other potentially hazardous foods)can be dried more safely by first curing them, with salt and/or with nitrates. It isn't hard, but you do need to know what you're doing. An excellent book on the subject is "Charcuterie" by Michael Ruhlman and Brian Polcyn.

    Starting with fruits and vegetables is a safe way to go.

    My dehydrator has a 600W element and is made of plastic that will withstand higher temperature.
    This Nylon box will have a hard time at these temperatures.
    Make sure the box is food grade.

    For meat drying, the guidelines recommends temperatures over 65°C. This will cook the meat, though.

    Heat input gets used to evaporate the water (which absorbs heat), so a low power will produce a slow drying, conducive to bacteria development. Remember that even if the outside air temperture is warmer, the surface temperature, due to evaporation, will remain lower, being just in the right breeding range for bacterias.
    You can prevent that with meat curing (add nitrates, an oxydizer, or celery juice, which is oftne five times richer in nitrates than the recommended added nitrate levels.) to prevent botulism, an anaerobic bacteria).

    You want the air inside the box to not be saturated with water vapor, or else, the evaporation process will stop. So you want to make sure a good quantity of air is bled out, but not too much as to cool down the enclosure.

    This is why the commercial units use 4-600W of heating instead of 60-100W as in the prototype above.

    Using a larger bulb, or more than one, increases the risk of fire, so the design must be carefully done.

    Most designs use a thermostat to set the temperature (so that you can bring and keep the meat up to safe temperature quickly) and coupled with a calibrated thermal fuse fuse that will blow at a certain temperature above the max thermostat temperature to premanently incapacitate the device if the temperature goes unsafely above the thermostat. (say, 50°C to 75°C depending on the location of the fuse.)

    http://www.thermal-sensor.com/Thermal-Fuse-RY_p934...

    Why permanently incapacitate (those thermal fuses are not resettable)? Because the condition that created the thermal fuse to blow are probably systemic, and thus, restarting the machine would still put it in danger of malfunction, possibly creating a fire.

    In this design, adding aluminum foil between bulb and any other inflamable material (plastic, even the dried-up food) is a very good idea for safety.

    We used an old version of the Little Chief meat smoker for years.
    (see images at

    https://upload.wikimedia.org/wikipedia/commons/thu...

    During the late fall, when the outside temperature was nearing freezing, we would put a ten-test box over the unit, and 1"styrofoam covered. It lost plenty of heat though the hot air convection. We also put a 150W light bulb inside to keep the temperature high. This came as a solution to having several batches of large expensive pieces of meat gone putrefied during the smoking process, despite suitable short (24h) curing, including curing solution injected into the meat.

    If you want to dry meat properly, the thinner it is, the faster it will dry (and stop bacterial action).

    I use a commercially available dryier because I find the air flow and temperature lead to very fast dessication, which is safer.

    I am quite that a very inexpensive dryer can be achieved faily easily. A thermostat costs only a few bucks at electronic/surplus warehouses, and a thermal fuse is only a buck. A more powerful light bulb (or two) are also inexpensive. For another 15$ in parts, you can have a very nicely performing machine, if properly designed.
    But I would not trust this one. This was a good first proof of concept, but please, AGAINST E. Coli's and Salmonella's sake, keep improving your design !

    Original ancestral pemmican was made with moose meat dried at below-cooking temperatures. But in those days, the meat was not as frequently contaminated by e. coli as industrial farming produces.
    If you want to raw-dry meat, make the process fast, use super-thin slices (1/8" or less) and use meat coming from properly managed grass fed, outside field-raised herds. Raising cattle inside in cramped quarters is asking for e. coli problems.

    About air flow: Maybe this would be better:

    Fan at one end of box, pulling air out;

    Light at other end, but I would add a few slots in the box so air would be pulled through circulate around the buld and be heated.

    Just my two cents worth!

    1 reply

    It's convection. A fan pulling air out would reduce efficency. A simple hole works for simple venting

    "The dog in the last picture was super critical."

    Haha. That was great. We all need a helper.

    1 reply

    True, she helped by checking if the glue was dry, with her tail. And nearly checked if the knife was sharp

    Nice project, thanks for sharing!

    I made one some time ago, to be used outsides, under the sun, to dehydrate fruits. I've made in a plastic box, with a glass lid over it. Made some holes to natural ventilation, and made a raise bed, with some wire screen (tiny holes) to let air, but not bugs in. It worked very well but I had one problem: the plastic left a bad taste on the fruits.
    I don't know if it will happen to your beef, but it's something to consider. Now I'm making one with a wooden box, using the same glass lid.
    I'll definetely use some fan as you did. Luckly I'll be able to use a small solar panel plus a joule thief to run a small fan.

    Lots of info missing here. The lamp and fan must have been wired in parallel. The fan sucks the air out of the box, I assume. Am I right?

    3 replies

    In parallell, yes. See pic and description in step 3.

    The fan blows air in. I left the lid ajar at the opposite end for this batch, but will cut vents for the next batch, I think.

    Let me know if you're having trouble with making anything else out

    Okay. Thanks for replying.

    No probs

    As others have asked, what is the wattage of the bulb? Do you know what the temp should be inside?

    1 reply

    Bulb is 60 w, don't know the temp. Technically, it's biltong rather than jerky, so salt and vinegar marinade, relatively cool and lots of air.

    I fabricated a dehydrator a few years ago but used the heating elements from an old bread toaster. Disassembled the toaster, pulled out the elements and mounted them on a small aluminum frame (careful here because you are fooling with open mains voltage so everything has to be mounted so as to not get near it. In my case, I enclosed the whole heating device in chicken wire covered frame, placed inside a wooden box with a glass window and of course vents to allow air to flow naturally around the meat. It was quite a bit of work to do this, but there was plenty of heat!! To control the temperature, I used a simple timer plugged into the mains, and programmed it to turn off and on at adjustable intervals. I don't have pictures, too long ago and I don't know what happened to it when we moved house a few years ago. I had a meat slicer and sliced the meat 1/8" to 3/16". Worked great.

    1 reply

    Cool, sounds awesome !

    Again, what is the bulb size, box size and does the fan blow out he air. Did it even work correctly? Were there any times recorded for anything?

    1 reply

    Bulb is 60 w, fan blows air in, Box is approx 10 litres. Dry time was 4 days total, but 2 days was with the meat as shown, after which I split it into thinner strips as the middle was still wet. Worked great.

    I just thought I should comment on the hangers which appear to be painted or coated with plastic. This coating is probably not intended to be used with food and may come off on the food.

    1 reply

    Yeah, was thinking that too, I've since swapped them out for some wire cooling racks