Does anybody else have trouble with the iodine test?

[Brew_Meister_General]

I can never seem to tell whether I am getting full conversion or not.

I put a few drops of iodine in a glass, add a few drops of wort but no matter what the liquid gets a bit darker and I can't tell whether this because of a small amount of starch still present or whether its just the yellow and red mixing.

As a result I end up mashing for 3 hours.

I should mention that as I use a boiler for a mash tun I have in the last 2 brews accidentally heated it up to 72c before trying to lower it to 70c.

 

[masonsjax]

Iodine doesn't really give you useful information anyway. It can tell you if there's starch present, but gives no indication of the fermentability of your wort. Alpha amylase breaks down starch very quickly. Beta takes a little more time to create shorter fermentable sugars, but iodine can't tell you that.

If you're having trouble getting your starch to convert, it's most likely either a pH issue, or you need to crush finer. Longer mash time is a workaround for one of these two problems.

 

[mongoose33]

My 11th batch is in the fermentor, and I've never used the iodine test. It seems to me that you should be able to tell how well you're doing just by checking the gravity. Based on my experience with 8 all-grain batches, a typical gravity of first runnings will be between 1.080 and 1.090. Since, when it's been that way, everything else has come out well, I don't worry about conversion; I'm getting it, and getting it in spades.

 

[jmcquesten]

When I do an iodine test, I put about a teaspoon of the wort (liquid only) on a plain white plate or bowl. Then I add a drop of iodine. If the iodine color stays the same but waters down a bit, the starch is mostly converted. If it gets darker or black, the conversion isn't complete yet. This only really works on lighter colored beers. If you're making a stout, porter, or other dark beer, you won't be able to see if it's black or not.

 

[doug293cz]

My 11th batch is in the fermentor, and I've never used the iodine test. It seems to me that you should be able to tell how well you're doing just by checking the gravity. Based on my experience with 8 all-grain batches, a typical gravity of first runnings will be between 1.080 and 1.090. Since, when it's been that way, everything else has come out well, I don't worry about conversion; I'm getting it, and getting it in spades.

Checking gravity of the wort in the mash is the way to go. It's actually quantitative (i.e. it will tell you what your conversion efficiency is.) Read more about it here.

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