If you need a starch, however, and you can have either sweet potato or potato, there's a really easy way to make your own sweet potato or potato starch. This method leaves you with remainders from the process that you can turn into sweet potato flour or potato flour, too!
I would link to the site I originally got this from (Tammy at homeschoolblogger.com) but it doesn't seem to be in existence anymore, sadly. So I'll just note where I got it from and jot down the directions here!
And the first thing is - it's really easy! I do this all the time.
Here are the directions from Tammy's website for sweet potato flour/starch:
- FOR MAKING STARCH OR THE FIRST STEP IN MAKING STARCH-FREE FLOUR. If you don't care about starch in your potato flour, skip to the last step. Otherwise, grate the potato/sweet potato very finely and place the wet pulp into a clean cloth that you have sitting in a bowl. Wrap up the pulp so that you have basically a sphere of pulp wrapped up in a cloth, twisted closed at the top.
- In this step you will be rinsing the starch out of the pulp by sqeezing the cloth bag of pulp over the large bowl to get the liquid out (which contains the starch). Then add clean water to the cloth bag of pulp by pouring water over the bag (while still over the bowl - you don't want to have anything coming OUT of the bag that you aren't catching!) and squeeze again to get out more liquid. Repeat until the water runs clear when you squeeze it out from the cloth bag of potatoes. The liquid will be cloudy white for potatoes, or orange for sweet potatoes. Next step will involve the liquid, but save the pulp for making potato/sweet potato flour – more on that later.
- Settling out and rinsing the starch is next. At this point you will need to place the liquid into the refrigerator (to keep the liquid from oxidizing or fermenting). Let it sit in there for at least 4 hours. Take it out as carefully as you can so as not to stir up the starch that has settled to the bottom. Pour off as much of the cloudy or orange liquid as you can without losing all the white starch at the bottom.
- Now add some clean water and stir up the starch. A spatula can work well to loosen the starch from the bottom. Then place back in the refrigerator for at least an hour. The starch will have settled again. Pour off the rinse water being careful not to lose the starch. Allow what water does remain to evaporate until you have dry starch. Collect this and store it once you are sure it is dry. I have not tried using heat/dehydrator at this phase. I do not know if the addition of low heat would change the starch or not. One sweet potato made almost 1/4 cup starch.
- THE PULP: How to Make Potato Flour: If all you are after is the flour and not any separate starch you can skip the steps above and merely dry the pulp with the starch in it. All you need to do is let the pulp dry out. Tammy had a grain mill, to processed the dried pulp, a Whisper Mill. One sweet potato made 1/4 heaping cup of sweet potato flour without the starch.
If you have to grate up potatoes and squeeze out a little of the liquid, like with my potater tots recipe, you can save the liquid just like the liquid in the above recipe, and save it, too. I do that all the time, building up my potato starch reserves a little at a time. :-)