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  • FrankN16 commented on oniume's instructable Food Dehydrator 9 months ago
    Food Dehydrator

    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 b...see more »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.

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