Author Topic: Iodine test for mash conversion  (Read 6715 times)

Offline malzig

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Re: Iodine test for mash conversion
« Reply #15 on: December 19, 2011, 07:39:01 PM »
I disagree that it is a useless test, it will tell you if there are major problems with your mash. It WILL tell you if there are any starches present in the wort.
It will tell you if there is a MAJOR problem with the mash.  What it won't tell you is if all the starches are converted.  Recent experiments in BYO comparing iodine test results and conversion by mash gravity showed that, in many cases, the iodine test was negative for starch long before conversion was complete by the gravity of the mash liquor.  I believe they showed that the iodine test can appear negative by 20-30 minutes, while conversion can continue for an hour or more.

Offline mabrungard

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Re: Iodine test for mash conversion
« Reply #16 on: December 20, 2011, 06:33:38 AM »
Would it really be "conversion" or "extraction" that was measured in the BYO testing.  Its probably possible to accomplish either one without fully completing the other.  I rarely perform an Iodine starch conversion test, but I always monitor my extraction gravity during each mash.  

I probably should check conversion. But as Malzig mentioned from the BYO testing, it appears more likely that you will achieve your conversion if the mash period is long enough to show that the gravity has stabilized.  Of course, this all goes out the window if the mash didn't have enough diastatic power or the mashing temperature(s) where incorrect or out of range.
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Offline mattc

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Re: Iodine test for mash conversion
« Reply #17 on: December 20, 2011, 06:36:33 AM »
As far as the iodine test goes, I say for the price of Iodine why not use it. I use the iodine that you buy in the drug store for like $2. I bought it 2 yrs ago and I am still using the same little bottle. I disagree that it is a useless test, it will tell you if there are major problems with your mash. It WILL tell you if there are any starches present in the wort. For instance if you have let the mash rest for n hour and you still are getting some purple tinge, it may be a sign that your themometers may be reading wrong or the PH is off and these factors may be inhibiting a full conversion. The downside, like Denny said, it will not tell you how the wort converted: into more dextrine or more fermentables. hope that helps some.

One of the main reasons I don't recommend is it that I've heard from so many people who keep mashing for 2, 3, 4 hours becasue the iodine test says they haven't converted.  In almost all of those cases, I believe they've just gotten a false reading.
I'm only speaking from my experience as that is all I have to go off of. I use it everytime I mash and have seen the difference between the iodine showing purple(starches present) and a negetive reading which is usually at the end of the 60mins. So far I have not ever had a false negative and it shows in the hydro samples after fermentation. I always have the full attenuation, not due to fact that I "made sure" with the iodine, but for the same reason the brewer at SN tests his conversion even though he is 99% sure. Its also the same reason i use 2 thermometers when brewing, reassurence I suppose.

For the record, I use a clean white porcelan bowl and can definitely see the difference between starches that are present and wort that has converted fully. Guess its just my process. ;) ....good discussion fellas! :)
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