Reason:

Since the family favorite GF bread recipe depends on potato starch which I cannot buy locally, I decided I would try George W. Carver's instructions on making my own. It was lots of fun. Even if you never want to make this for a bread recipe it would be a great hands on way to study George Washington Carver. I posted quite a bit from his book related to how to use the sweet potato just a few days ago.

Goal:

I wanted to learn specifically how to isolate the potato starch, but I also wanted to know how to make the flour too.

How To Isolate Potato Starch from White or Sweet Potato:

I have now made both white and sweet potato starch and flour. I am going to use the sweet potato for the pictures because the distinctive orange color makes the white starch so obvious in the final stages. I used only one sweet potato for the demonstartion so that it would be easy to see how much of the starch and flour to expect per potato that you process.

Step 1 -

Grate the potato very finely and place the wet pulp into a clean cloth that you have sitting in a bowl.

Step 2 -

In this step you will be rinsing the starch out of the pulp by sqeezing the bag of pulp then adding clean water and sweezing again until the water runs clear when you squeeze. In this picture you can see the orange liquid that results. For white potatoes, you can use the pulp to make fried hashbrowns by adding some salt and pepper with an egg to hold it all together. In this instance though, I saved the pulp for making sweet potato flour - more on that later.

Step 3 -

Settling out and rinsing the starch is next. At this point you will need to place the orange 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 orange liquid as you can without loosing all the white starch at the bottom. No add some clean water and stir up the starch. I used a turner which worked really 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 loose 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.

Here is a picture of the rinsing stage:

OK, Now. 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.

Here is the amount of dehydrated pulp you can get from one sweet potato.

I have a grain mill, so I processed the dried pulp in my Whisper Mill. Here is a picture of the flour. One sweet potato made 1/4 heaping cup of sweet potato flour without the starch. I would assume that you would end up with 1/2 cup flour if you did not remove the starch like I did.