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Old 07-06-2008, 05:41 PM   #1
Donasay
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Default Starch conversion problems

I have some problems with my starch conversions and think there might be two possible problems. I mashed in about an hour and a half ago and keep doing iodine tests, but conversion isn't complete. I mashed in and hit my temperatures almost exactly, so mash temp isn't the problem.

I have narrowed it down to two variables, first possiblity is that my grain got cooked in the back seat of my car and second is that I have bad iodine. I purchased the grain at my lhbs on friday after work and let it sit in the back seat of my car till this morning essentially letting it bake in the 120 degree heat inside the car all day yesterday. The other is that I have bad iodine, which I left sitting out in the sun for a day and a half last time I brewed.

I don't know what to do in this situation, but if it doesn't convert in the next 30 minutes I am going to mash out anyway and just brew as normal. Is it possible that the heat inside my car denatured the enzymes in this grain, or am I just being paranoid.

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Old 07-06-2008, 05:46 PM   #2
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Do you normally get a positive indication of full conversion when using iodine? Is it that this one brew is behaving differently? If so, tough call.

I stopped doing an iodine conversion test because I found it terribly unreliable (lots of false negatives).

Try recirculating until you get clear wort, then take an iodine test. Sometimes husk material or other suspended junk will really throw off the test.

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Old 07-06-2008, 05:54 PM   #3
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I do normally get indication, but I have no way of knowing false positive or false negative, I have gotten positive starch conversion after 30 minutes on previous batches, and sometimes it takes 2 hours.

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Old 07-06-2008, 05:57 PM   #4
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120 degree dry heat while the grain is dried is not the culprit, the malt is kiln dried at temperatures hotter than this for longer times before it's sold to you.

I agree with Fly that it's not likely the iodine but how you're using it, probably getting a bit of husk in the sample. Use the chalk method, place the drop of wort from your thermometer on a piece of sidewalk chalk and then apply the iodine to it, this lessens the risk of grain bits. once done, shave that piece of chalk off with a chisel or carpet knife to expose a clean piece for the next sample.

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Old 07-06-2008, 06:00 PM   #5
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I do normally get indication, but I have no way of knowing false positive or false negative, I have gotten positive starch conversion after 30 minutes on previous batches, and sometimes it takes 2 hours.
Well, it is possible that you cooked your grains in the car, although even 120 F shouldn't be enough to denature all your diastatic enzymes. I would suggest that if the starch test only shows a bit of reaction to the iodine, you are done. You might try a recirc to see if that changes anything.
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Old 07-06-2008, 08:52 PM   #6
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When I first started brewing AG, I did an iodine test for conversion and I ended up doing two our mashes. I then learned that I probably had conversion but the test was unreliable. I don't bother with iodine tests any longer. I mash for an hour and then sparge. I get decent efficiency and normal attenuation most of the time.
They say that modern malts actually convert in as little as 30 minutes.

One question: What is your grain bill? Depending on what you are using, the conversion time could vary.

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Old 07-06-2008, 09:57 PM   #7
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Well I just brewed with it and the gravity came out fine, it was 15lbs of marris otter and 1 lb of crystal 60. I was just really worried that I had cooked the grain by leaving it in the back seat of my car for a couple days. Additionally the iodine tests are always more accurate when the idoine is fresh.

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