Tuesday, March 10, 2015

Homemade Potato Starch

There are lots of uses for starch around the homestead: thickening stew or pie filling, making gravy, making edible glue (Katie says, "well, if you're going to eat it anyway..."), making cosmetics, powdering wigs, and so on.  Clearly, we need a way to make some homemade starch.  The tricky part is, most commercial starch comes from tropical plants like arrowroot or cassava, or from hard-to-process grains like corn, wheat, or rice.  Except potato starch.  Potato starch is made from something we can grow and process without too much trouble.  Ready...go!

The first step is to figure out how much starch we can expect to get out of our taters, so we can calculate a yield later on.  Since starch is denser than the rest of the potato, a potato's density is generally proportional to the starch content.  Using the displacement method...

...we found that our potatoes are 13.3% starch, averaged over five potatoes.  Data for the graph on the left came from here.

The next step is to get that starch out of the potato cells.  The starch is trapped inside the cells like a medieval princess in a dragon's lair , waiting to be eaten by the dragon in the spring (if princesses looked like oblong globules piled inside a vaguely hexagonal prism).  And we get to be the knight in shining armor.  (Photo Credit: "Potato Starch" by Philippa Uwins (CC BY-SA 3.0), via Wikimedia Commons)

 Fortunately, we wield the mighty Sword of KitchenAid

A few minutes later, the dragon is nearly defeated.  Now we just need to rescue the starch princess.

We do that by flushing the potato pulp with water and using the ol' t-shirt filter and squeeze technique.


We mix the pulp with water and squeeze out the milky-colored liquid three or four times until the water looks fairly clear (it looks white at first because it's carrying the starch granules with it).  We can keep rinsing and squeezing beyond that if we want, but then we begin to wander into the Land of Diminishing Returns.

Now we're left with the potato pulp (left) and water/potato juice/starch (right).

Pouring the water into something with a higher aspect ratio will help in the next step when we decant the juice.  The white layer on the bottom is the starch princess, which settles out on standing for a few minutes.

While the starch is settling out, we take the potato pulp, mix it with a chopped onion, egg, salt, pepper, garlic powder, and rosemary...

...and fry up some potato pancakes! (Or dragon burgers, whichever you prefer.)  Dragons: thank you for meddling in the affairs of homesteaders, for you are crunchy and good with ketchup.

Once it looks like no more starch is settling out of the liquid, we carefully pour the liquid into a pitcher, leaving a solid layer of starch behind. (If you splash and swirl the liquid while pouring, some of the starch will come with.)

We scrape the starch out onto a dehydrator tray with a fruit leather insert. Now we just have to drive off most of the water.  We want to not go to very high temperatures in this step, since the starch will start to gel around 64 °C (147 °F).  So we'll stick to the food dehydrator, like Mrs. Volfie suggests

Holy non-Newtonian fluids, Batman! One cool thing about concentrated starch-water mixtures it that they're shear-thickening.  That is, apply a force to them, and they act like solids.  Let them sit there, and they act like liquids.  Kind of a pain when scraping the starch out of the jars, but if you spill any on the counter, just grab that drop with your fingers and pick it right up!  You can also watch the solid transform back into a liquid, which is kind of apparent in this picture.

If some of the juice comes with the starch, it will form dark-colored parts when it dries.  But it won't make much of a difference in the final product.

Once it's powdered up, it still looks pretty white, like starch is supposed to.  Our final yield was 131 g starch from 2272 g (5 lbs) of potatoes.  At 13.3% starch, that many potatoes should have given us 302 g starch, so we ended up with about 43% yield, based on the theoretical maximum.  Industrial processes give about 90% yield or more, so we're not quite there.  But industrial processes also don't give potato pancakes as a byproduct, so we've got that going for us.

If you search online for what to do with the juice, you'll find a plethora of sites with unsubstantiated claims about the health benefits of potato juice (although there may be some merit, if you dig deep enough).  They also usually recommend blending the potato juice with other components, such as lemon juice and honey, to mask the flavor.  It's not that bad, but we haven't found a reasonable combination of lemon juice, honey, and potato juice that render it satisfying.  It's better with more strongly-flavored ingredients, like chai tea concentrate and hard liquor.

How do you make starch on your homestead?  Let us know in the comments section below!

2 comments:

  1. Cool! I have a sudden craving for potato pancakes. ...

    ReplyDelete
  2. Very interesting post. Actually it hadn't occurred to me to try my hand at making starch (although I dearly love potato pancakes. The potato juice I'd probably use in baking). If I need a thickener I find myself using flour, which I still buy so I suppose that's cheating!

    ReplyDelete