If you’re doing a cooker grain wash and trying to figure out if all of your starches have been converted, there’s an easy way to find out. It’s called the iodine test, and all you need is some iodine, which can be purchased at your local drug store or supermarket. There’s also a Cheat Sheet at the bottom of this blog if you want to save or print it.

What is an Iodine Test?

The iodine test is used by adding iodine to a solution to test whether or not the solution contains starch. I’ll spare you on the scientific mumbo jumbo—all you need to know is that iodine changes color in the presence of starch. It becomes a dark indigo/blue/black color, making it obvious if you still have starches in your mash that haven’t yet been converted.

How Do I Use Iodine To Test Starches In My Mash

The test itself is simple to do, but there are a few things you need to keep in mind if you want to do the test correctly.

  1. First, the liquid must be cool in order for the iodine test to work properly. One method is to put an empty saucer in the fridge so that the saucer will be nice and cold for when you’re ready to perform the test. 
  2. Take one Tablespoon of your mash liquid and add it to the saucer, gently stirring it with the spoon in order to help it cool faster. 
  3. Add one drop of iodine to the saucer with your liquid. 
  4. If the liquid doesn’t change color, then all starches have been converted, and you can continue with your wash.
  5. If the liquid changes color to an intensely dark blue/black, then there is still starch in there that needs to be converted. You may need to allow it to sit longer and/or add more alpha amylase to your mash in help convert the starches into simple sugars. Also be sure that it stays within the recommended temperature range for alpha amylase, which is between 152°F to 158°F.

How To Use Iodine To Test If Your Starches Have Converted

And that’s all there is to it! If you have any other questions, feel free to contact us through the website or send us a message through Facebook. Happy Fermenting!