Iodine Test

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ayoungrad

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I posted this question in the middle of another (not entirely relevant) thread and did not get an answer.

I do BIAB. Before I did my first few BIAB batches I bought Tincture of Iodine for starch conversion testing. I looked for Lugol's but could not find it (thanks to drug addicts everywhere) but it is my understanding that the main difference between the two is that Lugol's does not use alcohol for solubilty and that both should work for starch conversion testing.

I say all of this because I ran the test several times on the first few BIAB batches I did. I would take a small amount of the wort, place in onto a white plate and then put 1-2 drops of the tincture into the wort. Early in the mash it would turn black immediately but even up to 2 hours into a mash, it would still slowly turn a "light" black. I never went more than 2 hours for any of these mashes despite the absence of a "clean" starch test.

I have since stoppped testing because I found it so unhelpful. I run one hour mashes and have had great/expected efficiency, attenuation and FGs. And the beers have been good. (BTW, on my original posting yesterday I only mentioned efficiency. I woke up this morning realizing how almost irrelevant efficiency is to this discussion.)

So why would I continue to get a semi "incomplete" result with iodine testing? My only thought (aside from the possibility that I'm doing something completely wrong) is that I'm getting little bits of grain in my sample which will never completely convert to sugar. But if that is the case, wouldn't everyone fail to get a complete conversion iodine test?

Thanks in advance.
 
The reason most people don't do iodine tests is because most people aren't formally trained to read one. It's actually something that takes a lot of training to do accurately.

"So why would I continue to get a semi "incomplete" result with iodine testing? My only thought (aside from the possibility that I'm doing something completely wrong) is that I'm getting little bits of grain in my sample which will never completely convert to sugar."

Yes, you're right. Draff will cause a false-positive in the iodine test.
 
Most people that mash grains do that in a mash tun and not a BIAB system. Runnings from a mash tun will turn very clear and without any big particles, so a iodine test always work.
I have tested many times and didn't do anything special, I'm not formally trained, and I always got good results.
May be one using a BIAB process could pass the wort thru a coffee filter first before testing.
 
Thanks for the link and thanks for the all the reponses.

Learned a new word... I had never heard of draff before. The article does say this will cause a false reading.

I was taking my sample from outside of the bag so it is sort of filtered. There are never any large particles, just tiny ones. But maybe a coffee filter or the like would be a helpful idea to try. I'll have to try it.
 
Particles in the mash liquid will always test deep blue.

The best way to get a meaningful test is to take some liquid from the mashing vessel (tun, bag....) up with a teaspoon. Try to exclude husk material. Place a drop of this liquid on a smooth, white porcelain plate. Place a drop of tincture of iodine next to the drop of wort. The two will run together. Read at the interface between the drops. Ignore dark specs from particulate matter in the wort.

If the plate is one you eat from be sure to wash all the iodine off and run it through the dishwasher before using it to serve food again.

If the mash:

1. Turns dark
2. Becomes easier to stir
3. Tastes sweet

you don't really need an iodine test. It has converted.
 
If the mash:

1. Turns dark
2. Becomes easier to stir
3. Tastes sweet

you don't really need an iodine test. It has converted.

This doesn't make sense to me.
An iodine test is to know if one had a "FULL" conversion, meaning no starches left.
Conversion will alsways happen, a full coverstion, not always.
 
I guess what I should have said is that after you have done a few of these you will stop doing them because you will always have some pink/orange from residual dextrines, will have noticed that your efficiencies are good, will have noted from malt spec sheets that saccharification times are from 10 - 20 minutes and will stop wasting your time on iodine tests. If you get the three indications I mentioned in the last post and let the mash sit for 20 minutes at a reasonable temperature, you will be as converted as you are going to be. I can't think of anything that would cause a mash to go to 75% of normal and then not the rest of the way (recognizing, of course, that completion is approached asymptotically). As part of the learning process, by all means do iodine tests but eventually you will find they aren't telling you anything you don't already know.
 
That is essentially what I've done. Except I mash for 60 minutes.

You only do 20 minutes mashes? For all mash temps? For all mash thicknesses?
 
Not really. Most of my brewing is lagers. The length of the "rest" is, I suppose, the sum of the time you let it sit plus the time it takes to pull the next decoction and get it started upwards in temperature. Then throughout the the decoction 60% of the mash sits at saccharification temp. Thus 40 % of the mash gets a 30(?) minute rest and 60 % gets an hour and a half. When I do non German ale or stout I guess I let it go about 40 minutes knowing that most people let their ales go longer but confident that I've gotten about all I'm going to get. An iodine test never showed anything other than conversion as complete as one can detect with an iodine test after 20 minutes or so.
 
If the mash:

1. Turns dark
2. Becomes easier to stir
3. Tastes sweet

you don't really need an iodine test. It has converted.

I'm gonna agree with AJ Delange on that one. Once you've done a dozen or so mashes, you'll get a feel for how they work.
 
I have done my fair share of thinking about mash conversion and the iodine test. Here are a few points:

- you should dilute the iodine tincture or iodophor with alcohol at a ratio of 10:1. This will significantly lighten the color of the tincture and you don't end up wondering if the color comes from the iodine or the reaction with starch.
- consider doing the test on a piece of chalk or the gypsum inside drywall. You only add a drop of wort and add a drop of iodine. If there is a color reaction you'll start to see the outline on the spot from the wort.
- the wort that you bring to a boil has to be iodine negative in order to avoid a starch haze, but an iodine negative test does not mean that mashing is complete.
- in practical mashing malts don't fully convert in 20 min. They generally take longer. How long it takes depends on factors like crush, temp, mash thickness and pH
- even the 15 min number from malt analysis sheets doesn't mean that it took 15 min for the malt to convert in the lab. In the congress mash it means that it took 15 min to convert after that mash schedule hit the 70 C mark, which is after 55 min of mashing. Check out page 32 of the presentation I gave at last year's NHC (http://braukaiser.com/download/Troester_NHC_2010_Efficiency.pdf)
- The iodine test only tests for starch and large dextrins in the wort. Once it turns negative continued mashing can still lead to the release of dextrins and sugars into the wort which increases your efficiency.

There have been a few Basic Brewing Radio shows on this topic recently which you may want to check out. In addition to that I do recommend reading my recent article on iodine testing: http://www.braukaiser.com/wiki/index.php/Iodine_Test ( I saw that posted earlier, Thanks DeafSmith ).

Here is a blog entry with some data that backs up my points: http://braukaiser.com/blog/blog/2011/03/04/conversion-progress-in-a-single-infusion-mash/

BTW, I was able to buy Logol's iodine: [ame]http://www.google.com/search?q=lugols+iodine&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:eek:fficial&client=firefox-a#hl=en&client=firefox-a&hs=GKk&rls=org.mozilla:en-US:eek:fficial&tbs=shop:1&&sa=X&ei=oMFxTdrANcWqlAeR2cRi&ved=0CFkQBSgA&q=lugol%27s+iodine&spell=1&biw=1366&bih=546&bav=on.2,or.&fp=7e0c973786b8478e[/ame] I don't remember the store, though. Iodophor works equally well.

Kai
 
Thanks. I read through your posted article. I think it would be interesting to test future batches using your techniques. I have not tested the last 5 or 6 batches (I mashed for 60 minutes and assumed they were done). These batches turned out great but I'm always up for tweaking things to gain even more control over my results.
 
I think that testing the mash gravity and correlating it to the maxium that is possible for the given mash thickness gives you more information about mash progression than the iodine test.

Here is a chart of the highest possible mash gravities. Keep in mind that the mash has to be stirred to even out the sugars before the gravity can be tested:

First_wort_gravity.gif


Kai
 
I realize it was not your main point but I had never heard that there was a maximum SG based on mash thickness. Interesting.

As far as SG and conversion. So you use gravity in lieu of the iodine test? Will starch contribute to SG or is it still relatively insoluble at mash temps? I'm realizing now that I must have been incorrectly thinking that starch was soluble in warm water.

BTW, do you use a refractometer or a hydrometer for testing your mash? Just asking because I was thinking about getting a refractometer.
 
I realize it was not your main point but I had never heard that there was a maximum SG based on mash thickness. Interesting.

You won't find this in any of the home brewing literature. Even in the professional brewing literature I have not seen this mentioned. But if you think about it, it there has to be a limit since the amount of starch and the amount of water is limited. But it's difficult to calculate with the commonly used gravity points based efficiency calculation. Using weight percent of extract (i.e. PLato) makes it easier.

As far as SG and conversion. So you use gravity in lieu of the iodine test? Will starch contribute to SG or is it still relatively insoluble at mash temps? I'm realizing now that I must have been incorrectly thinking that starch was soluble in warm water.
The iodine test and the mash gravity test both test different things. Though it is unlikely to get a positive iodine test when you are close to or at the max mash gravity, you can have a negative iodine test w/o having converted all starches. The unconverted starches are still inside grit particles and thus don't show up in the iodine test.

I'll have to check if starch contributes to gravity measured by a refractometer.

BTW, do you use a refractometer or a hydrometer for testing your mash? Just asking because I was thinking about getting a refractometer.
No, you don't need a refractometer. In fact, my work on this was done when I didn't own a refractometer yet. I took the gravity readings with a hydrometer. But admittedly, a refractometer makes taking these readings much easier.

Kai
 
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