Cut the ginger into very thin slices- the thinner, the better. You can do this with a knife, if that's all you have available, however, I like to use my mandolin for this.With thin, even strips, you'll find that the dehydrating goes quickly and evenly as the strips are all uniform.
Next, line the thin slices on a baking tray or a dehydrator tray, making sure that the slices don't overlap at all.
To Dry in A Dehydrator: Simply dehydrate at 40ºC/100ºF for about 4-5 hours.
To Dry In The Oven: When using an oven it is best to use the lowest temperature possible, to avoid burning/cooking the food. Dry at 80ºC/176ºF and needs around 2.5 hours to dry. For best results, place the baking tray on the lowest rack. If your oven won't go as low, then you can crack open the door slightly. This helps the liquid to escape the oven as well as brings down the overall oven temperature.Check on the ginger every 20 minutes or so, to make sure that it isn't burning.*
Bonus: To Air Dry: **Simply place on a large dish by a sunny window and leave for 3-4 days. Check the progress every day. They may be ready sooner/later depending on the weather, amount of sunshine, temperature, etc.
To air dry, simply place the pulp on a baking tray or large dish and leave in a dry, well-ventilated area for 3-4 days. Alternatively, use an oven or dehydrator in similar ways that I described above just make sure to continue to check on the pulp as the time will differ depending on if you used it straight from juicing vs. from frozen and thawed, etc.
How To Know The Ginger Is Ready
No matter which method you use, what you're looking for is completely dry ginger. It needs to be a 'crunchy' kind of dry, that snaps rather than bends.****
Grinding The Ginger Into Powder
Place the dried ginger slices or dried ginger pulp into a grain/seed grinder or into a food processor/blender and grind into a fine powder.
It's best to sieve the powder to collect any larger pieces which you can then grind again.
You'll be left with a super-fine ground ginger powder that you can then transfer into an airtight glass jar and store for around 6 months. You could also store it in the freezer for even longer - likely 12 months or more.
* Depending on your oven, and the thickness of your ginger slices, this may take more or less time.** I've found that this method works best in a dry climate - when sunny. Humidity tends to just make food spoil and get moldy. However, if you live somewhere it's dry, is having good weather, and have patience, then this method allows you to dry out your ginger without the use of any heat at all.*** I like to store all the pulp from juicing ginger in the freezer until I'm ready to dry it out. However, you can also just use the pulp from a single session of juicing to dry into a ginger powder.**** Any moisture left in the ginger will cause it to become paste-like when ground, instead of a powder. It will also impact the shelf life- so make sure there's no bend to the ginger before moving to the next step.You can actually use the dried ginger slices and fresh or dried ginger pulp to make homemade ginger tea too!
Recipe on Alphafoodie: https://www.alphafoodie.com/how-to-make-ginger-powder-two-methods/