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Home Brew Forums > Home Brewing Beer > Brew Science > Why isn't an Iodine test the "defacto" standard for mash time?
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Old 04-16-2009, 01:41 PM   #11
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How does pH indicate complete conversion? Don;t think I have ever heard or read that suggested. I know pH facilitates the enzyme activity in optimal ranges.
Yeah ignore me, I don't know what I was thinking about. Probably half asleep at work. Yeah that's it.
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Old 04-16-2009, 02:16 PM   #12
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Yeah ignore me, I don't know what I was thinking about. Probably half asleep at work. Yeah that's it.
I do that too.
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Old 04-16-2009, 03:01 PM   #13
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I meant Lack of Iodine at home. I never think about using an iodine test until I see mention of it on here. Never on brew day or before brew day to buy iodine.

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Old 04-16-2009, 03:45 PM   #14
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I have Iodine and I almost never use it and I almost never mash for more than an hour and often rest at low-ish sacc rest temps. When I do decoctions I test the decoction for conversion and it's usually starch-negative in 10-15 minutes...but that's resting at about 158 F or so. I've never had to go more than 15 minutes converting a decoction to starch-negative.

I used to always test but after a bunch of tests with not one being starch-positive I just stopped doing it for the main mash.

Plus, when you mash-out at 168 F or 170 F you don't denature all the enzymes anyway...the alpha-amylase are actually in turbo-mode throughout the sparge...making sure the job is complete.

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Old 04-16-2009, 04:42 PM   #15
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I meant Lack of Iodine at home. I never think about using an iodine test until I see mention of it on here. Never on brew day or before brew day to buy iodine.
That is where my big bottle of otherwise useless to me Iodophor comes in handy.
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Old 04-16-2009, 07:24 PM   #16
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This is a good subject to elaborate on. Let me try to put this iodine test thing into the big picture:

The wort that is brought to a boil has various requirements that it needs to meet. For one it should not contain any starch or long dextrines. Those are or will become insoluble in the presence of alcohol and create the so called starch haze. A brewer can test for the presence of starches and dextrins with an iodine test and the wort should show no color reaction with iodine. At this point it is said to iodine neutral. Large breweries even do it with photometric means which simply measures the light absorption of a wort and iodine mixture. Another requirement is the fermentability of the wort. I.e. the ratio between fermentable sugars and total dry weight of extract in the wort.

Both iodine neutrality and fermentability require enzymes to get them where we want to have them. That’s what the mash is for although you should keep in mind that the enzymes, a-amylase in particular, are still active during the lauter and in the kettle until the wort hits about 180-190F. After that there is no more change and if there is a problem with excessive starches/large dextrins it cannot be fixed unless you add more enzymes.

Fermentability cannot be easily checked by a simple test that is fast enough for you to take immediate action. But iodine neutrality can. It tests if there are any starches/large dextrins left in the sweet wort. It cannot check for full conversion b/c it doesn’t tell you if there are still unconverted starches in the spent grain. But that is not that important as long as these starches don’t make it into the kettle w/o being broken down by the enzymes.

60 min mashing is a quasi standard for home brewing. Mostly b/c it works for most mashes and keeping this variable constant simplifies things. But there is nothing wrong with mashing shorter or longer as long as your fermentability, iodine neutrality and efficiency goals are met. I think the 60 min are based more a historic and pragmatic background than on any empirically evidence.

Why do I advocate an iodine test for every mash? B/c it is good practice. Just like checking your mirrors when you change lanes even though it is 2am and you are the only one on the highway. The test is easy and quick enough and while it doesn’t give much valuable information if it is negative (b/c you expected that) it is very valuable to know if you mash tests positive with iodine (negative is a good thing and positive a bad thing not that intuitive but the same with getting tested for a disease ). The latter can easily happen when you push the boundaries w/ respect to mash time, mash temp or diastatic power. I know for example that the iodine test is a very important tool when using large amounts of dark Munich malt (e.g. 100%) in a mash as this malt is enzymatically rather weak and iodine neutrality after 60 min is not a given.

If the mash tests positive for iodine you may give it some more time, add some lightly kilned malt (i.e. fresh enzymes), check the pH or simply note the fact and keep on brewing. Maybe it turns out fine. At least you have one more data point for troubleshooting problems. Those beers are called “Blausud” (blue batch) in German brewing.

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Old 04-17-2009, 01:36 PM   #17
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Good info Kai, You are a great attribute to this community! Maybe I'll pick a bottle of iodine. you just put a drop on say a paper plate, then a drop of wort onto that?

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Old 04-17-2009, 02:55 PM   #18
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Great info Kai! I'm utilizing your method of checking every batch. I started doing this because I switched to StarSan and have a small bottle of Iodophor sitting on the shelf. Only using a few drops to test each batch, my small bottle will likely go bad before I use it all.

I've messed around a little with taking tests throughout the saccharification rest. I haven't really used the info to see if I can cut mash times though. I've noticed that wort I draw off the top is converted fairly quickly. Probably withing 30-45 min. I do notice that if I take some grain early on, mash it up good on a white plate, it tests positive. That makes perfect sense.

This topic begs the question. Is any type of iodine ok to use? Drug store iodine and Iodophor are probably the most common and easily obtained.

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Old 04-17-2009, 03:21 PM   #19
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Good info Kai, You are a great attribute to this community! Maybe I'll pick a bottle of iodine. you just put a drop on say a paper plate, then a drop of wort onto that?
Try that with just water first.
I'm not sure that paper is neutral wrt iodine.
I use a piece of white ceramic.
Others use a piece of sidewalk chalk.
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Old 04-17-2009, 04:27 PM   #20
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This topic begs the question. Is any type of iodine ok to use? Drug store iodine and Iodophor are probably the most common and easily obtained.
I think so. If it is made for desinfection purposes then it should work. The iodine that kills the germs is also the iodine that stains the glucose helices.

There is some info of the reaction here: Carbohydrates - German Brewing Techniques

I took most of the info from here:

Starch - Iodine

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