Failed iodine test

[Brewmenn]

For the first time after about 20 of so all grain brews I have one that has failed the iodine test. It's been going for over 2 hours and is still turning black.

I am using a 5 gallon water cooler for a mash tun. I have been adding hot water to keep the temperature up, but it is now full.

I am attempting a Gose Beer for the first time using a recipe from the LHBS.

The grain bill is:
5.75 lbs pilsen avangard malz premium
2 lbs wheat avangrad malz premium
2 lbs acidulated malt.

Any advice to save this?
What actually happens if there's starch in the wort?

 

[Silver_Is_Money]

Avangard Pilsen and Avangard Wheat are both listed at 76 Lintner (250 WK) minimum. I assume acid malt is zero Lintner. The mix overall should be an acceptable ~60 Lintner.

But you are attempting to mash while in the neighborhood of pH 3.3 to 3.4, and I don't know what impact that might have on the active amylase enzymes.

Did you perhaps dough in at above 168 degrees and thereby deactivate the enzymes? Bad thermometer?

All I can suggest is adding Amylase enzyme powder at about a TSP per gallon.

 

[doug293cz]

Avangard Pilsen and Avangard Wheat are both listed at 76 Lintner (250 WK) minimum. I assume acid malt is zero Lintner. The mix overall should be an acceptable ~60 Lintner.

But you are attempting to mash while in the neighborhood of pH 3.3 to 3.4, and I don't know what impact that might have on the active amylase enzymes.

Did you perhaps dough in at above 168 degrees and thereby deactivate the enzymes? Bad thermometer?

All I can suggest is adding Amylase enzyme powder at about a TSP per gallon.

If your pH estimate is correct (and I have no reason to believe it isn't) then that is probably the culprit. 2 pH outside the optimal range is huge. I would imagine it would really slow down conversion, and might denature the enzymes faster than normal.

Brew on

 

[Brewmenn]

It's possible the temp was high at dough in. I think my thermometer has been sticking some. I usually dough in at around 170° which usually leaves me around 154°. This one was around 158° so that might be the problem.

I don't have any Amylase enzyme powder and the stores are closed so that's not an option, but I will get some of that if this ever happens again.

I'll give it a few more minutes and continue with the process and see what happens.

 

[day_trippr]

Jeeze that does seem like an extraordinary amount of acidulated malt.
What's up with that?

Cheers!

 

[Silver_Is_Money]

I just read a bit about the process of making Gose, and the general method is to mash for 60 minutes (achieving full starch to sugar conversion) before adding the whopper load of acidulated malt, and then lastly add the acidulated and mash for an additional 45 minutes.

After the addition of the acid malt and the second mash, I have no idea if it would fail an iodine test at that juncture, but based upon your experience I strongly suspect that it very well might. But if so, this is apparently OK.

Aside #1: The first phase of the mash should be adjusted to roughly pH 5.4 as for any normal mash.

Aside #2: To properly match the style the grain bill is advised to be at least 50% wheat malt.

 

[Brewmenn]

Thanks for the advise, I will try that if I decide to try to make this beer again.

It never did show full conversion, but since I had little to lose I went ahead and boiled it and pitched the yeast. It is now happily bubbling away like normal.

I found it interesting but also frustrating that my internet searches for a lot of information on the how/why/when of performing the iodine test , but hardly anything about what to do about it if it fails and what effect it has on the finished beer.

I should be able to answer that last part in a few weeks.

 

[Silver_Is_Money]

A failed iodine test is a very dark. Almost jet black. Is that what you were seeing?

If you were seeing some level of mild darkening, but not "hit you in the face" pronounced, it was probably passing the iodine test.

 

[Brewmenn]

Looks pretty dark to me.