Iodine-starch test

[Pyg]

During my last few brews I have found my mashing (actually BIAB) has missed my target SG. I generally mash about 60-90 min around 154 (but can vary depending on recipe).
I have heard a few people on the interwebs suggest using iodine test to check starch has been converted

I am guessing that if the test shows you have not converted all the starches to sugar you continue mashing.
I read an article (posted below), but is this something people generally do with positive results?

And is the iodine used the same stuff you buy in the bandaid aide section of the grocery store?
http://www.-homebrew.com/starch-conversion-test.html

 

[RM-MN]

The iodine test will tell you if you still have starched in the grains that are not converted. Take a sample with mostly grains and add a drop of iodine (yes, the gorcery store or pharmacy stuff). It will turn the grain particle blue if there is still unconverted starch. At that point you can either mash longer (a 90 minute mash is pretty long, longer may not get you much) or just suck it up and drain the tun.

What you can do on the next batch is make sure it is milled finer. Since that may lead to a stuck mash or sparge, add some rice hulls or switch to using a bag for the filter.

I've done some test batches using iodine and a very fine grind from my Corona mill and get negative indications from iodine in less than 5 minutes so that tells you that if your iodine turns blue at 60 minutes you need a finer milling.

 

[Qhrumphf]

If your mashing parameters are in line (crush, pH, temp, diastatic power, water to grist ratio, etc, are not SEVERELY out of whack), an iodine test isn't gonna tell you a whole lot. The initial chopping up of starch particles occurs quite quickly. I stopped doing iodine tests long ago because they never showed remaining starch after more than a few minutes.

However, just because the starch is converted doesn't mean that sugar breakdown into your desired fermentation profile is complete. In other words, you can mash at 147, have "complete conversion" to iodine rapidly, but it may take 90 mins for the enzymes to break enough down to be as fermentable as you want.

As far as "complete conversion" you should check gravity, not with iodine. There's a direct relationship between gravity and water to grist ratio- thicker mashes will read higher than thinner ones. There are target figures for "full conversion" and you should ideally reach 95%+ of that level, or your mash isn't ideal (with grain crush being the #1 culprit). Braukaiser has a chart that I'd link if I weren't on my phone but can easily be googled.

 

[Pyg]

I usually double or triple mill my grain, I find with BIAB it helps me hit my numbers.

I have never really used rice hulls, just allowed the bag to drain and run some hot water over it to get what ever is left in bag, out.

Am I better off adding 1# rice hulls, taking a gravity reading at 60 min, using a temp conversation chart, if I don’t hit numbers continue mashing for 30 more min (90 total)?

 

[Calder]

60 minute mash - you should be done. I'm done and draining at 30 minutes.

I tried the iodine test a couple of times, but it didn't show anything. Since then I just check gravity.

What is your process?
- How fine is the grind?
- How do you check temperature?
- Have you checked your thermometer with other thermometers?
- Have you just started mashing, or have you changed something recently?
- What efficiency are you getting, and what were you getting before?
- water grain ratio.
- Etc.

 

[atoughram]

I always do a Iodine test - a creature of habit I guess.

I've only gotten negative results a few times - it turns nearly black when there is starch present.

 

[tgolanos]

...just allowed the bag to drain and run some hot water over it to get what ever is left in bag, out.

I used to have similar SG issues when I sparged like this. I moved to batch/dunk sparging and it solved my issues. 22.5L of water for the mash and 9L for the batch sparge. I let the grains sit in the sparge water for 10 or so minutes.

One other thing to consider is what kind of grain are you using? I had trouble hitting my numbers with dark beers until I started steeping the dark grains separately from my base malts. My guess is it had to do with mash pH.

 

[RM-MN]

I usually double or triple mill my grain, I find with BIAB it helps me hit my numbers.

I have never really used rice hulls, just allowed the bag to drain and run some hot water over it to get what ever is left in bag, out.

Am I better off adding 1# rice hulls, taking a gravity reading at 60 min, using a temp conversation chart, if I don’t hit numbers continue mashing for 30 more min (90 total)?

Rice hulls are only needed for a conventional mash tun where one would need intact hulls for a filter bed and the finer milling of the barley would tear up the hulls too much. With BIAB the bag takes the place of or augments the filtering of the barley hulls so no rice hulls are needed.

 

[RM-MN]

I used to have similar SG issues when I sparged like this. I moved to batch/dunk sparging and it solved my issues. 22.5L of water for the mash and 9L for the batch sparge. I let the grains sit in the sparge water for 10 or so minutes.

One other thing to consider is what kind of grain are you using? I had trouble hitting my numbers with dark beers until I started steeping the dark grains separately from my base malts. My guess is it had to do with mash pH.

Your grains don't need to sit in the sparge water for that long. The sugar is already there, ready to be washed off the grain. A quick, vigorous stir and the sparge is done.

 

[brandonlovesbeer]

Here you go. Here is a video I posted about how to do the iodine test.

https://youtu.be/1JcuWApYARE

 

[Smellyglove]

What is your target OG? Your own recipies, or someone else's? If you mash "normally", then there's nothing wrong, you just need to add more grain. Adjust your preboil efficiency. The iodine test will only show if the available starches has been converted. If you mash at 65C for an hour, you will most probably se a negative test before half an hour, depending on technique, it might show negative after ten minutes. However, if you raise your temp to 72C, you will get a positive reading, because not all starches are available at lower temperatures. Some of the granules need higher temps to dissolve. So you're only measuring if the starches at your mash temperature has been converted (available starches).

 

[Pyg]

60 minute mash - you should be done. I'm done and draining at 30 minutes.



I tried the iodine test a couple of times, but it didn't show anything. Since then I just check gravity.



What is your process?

- How fine is the grind?

- How do you check temperature?

- Have you checked your thermometer with other thermometers?

- Have you just started mashing, or have you changed something recently?

- What efficiency are you getting, and what were you getting before?

- water grain ratio.

- Etc.

-I have my grain double if not triple milled
- I use a long brew thermometer, which I checked with another cooking thermometer
-I have been doing a BIAB for about 2 years. Sometimes I hit my target, some times I don’t, once or twice I exceeded my target SG
-I usually mash with 3 gallons.

-my process is to mash around 152F, for an hour. Unless the recipe calls for a different temp.
After an hour I pull the bag and rinse with 170f water.

I find I miss my targets when I am trying to make higher AbV beers (anything above 8)

 

[Smellyglove]

I find I miss my targets when I am trying to make higher AbV beers (anything above 8)

You need to do some reading and research about high grav beers. When you understand the correlation between all those things that makes up "efficiency", and implement that understanding into a high grav beer, you'll start to hit your targets.

 

[RM-MN]

-I have my grain double if not triple milled
- I use a long brew thermometer, which I checked with another cooking thermometer
-I have been doing a BIAB for about 2 years. Sometimes I hit my target, some times I don’t, once or twice I exceeded my target SG
-I usually mash with 3 gallons.

-my process is to mash around 152F, for an hour. Unless the recipe calls for a different temp.
After an hour I pull the bag and rinse with 170f water.

I find I miss my targets when I am trying to make higher AbV beers (anything above 8)

The two colored sentences should tell you something. What it tells me is that you are not getting the grind you need and that the only way you are going to get consistency is to own the mill and not let anyone else touch it.

Owning a mill for doing BIAB need not break the bank. Corona mills are cheap and do a good job for BIAB. Once you get one and set it properly you won't need the iodine test because you won't have any starch left to convert at the 60 minute mark. My grains test negative in less than 5 minutes. However, don't try a really short mash even if that happens to you. 30 minutes gives me full conversion and full flavor extraction from the grains. Shorter than that can leave you with full conversion and flavorless beer.:rockin: