Conversion test with iodine and picture.

[brewkinger]

So this is my first time checking this mostly because I was bored and wondering.
I have always hit my numbers or very close, but thought I'd pass the time and boredom with a learning moment.

I used Iodophor and got no bits in my sample.
Put a couple drops of iodine into the the mix and it changed to a rusty brown color.

Is this a positive test for conversion? From what I have read, it seems that it is.

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[brewkinger]

I'm going to assume that this is good. I base this on the fact that according to BS, I hit a record 87.5% mash efficiency.
So this must be a positive starch conversion test...lol

 

[IslandLizard]

From what I understand, yes and no.

The wort (liquid phase) can be totally converted, but the grain bits themselves can still contain convertable starches, either not solubilized or still locked inside the beta-glucans/protein/pentosans matrix particularly in low- or undermodified malt or raw grain.

I also add a small drop of Iodine to a teaspoon of grist on the plate, and check the runoff. If dark blue it's not done.

 

[brewkinger]

From what I understand, yes and no.

So what part of my experiment was the yes and what part was the no?

I picked all the little bits of grain out before testing.

The drop of iodine turned dark when it first hit the wort sample but immediately went reddish brown and rusty colored.

Like I said, given 87% efficiency I have to assume that I converted starch into sugar.

I even added another sparge gallon and checked gravity and it was still 1.020ish

 

[IslandLizard]

I'd say the no part is you didn't test the runoff from the grain sample itself.

 

[brewkinger]

Test the little bits of grain... is that what you mean?

 

[kanzimonson]

I test every batch with iodine. I never test the grist. I also never mash out. If you combine all these things, you'll start to notice that conversion appears to be done after about 20 minutes. So I started lautering at the ~25min mark in my beers and have saved a bunch of time in my brewing.

Conversion continues during the ~30min runoff, and also as the wort is heated in the kettle. I get full attenuation with my batches, and am so glad to save on my most expensive brewing ingredient: time.

 

[brewkinger]

Hopefully this works.... Thanks NorCal.