Iodine test shows starch left in grains

[Horseflesh]

My mash efficiency is typically around 75%, and it doesn't vary much no matter what kind of stirring or temperature steps I may try. If I do an iodine test on the wort, I don't see any black, so I appear to be converting all the liberated starch into sugar.

Today I tried smooshing some of the spent grain with a spoon and dropped iodine on the husks--there was an obvious black color. I take this to mean that my crush could be better, because starch was still locked up. Is that a fair assessment, or would we expect to see some black from smooshed spent grain even with a highly efficient mash?

I'm using an electric single vessel system with a PID and wort recirc pump. I mill at the LHBS, and they tell me the gap is .045. I do double mill, which boosted mash efficiency from about 70% to 75%. I would like to improve my efficiency if there are easy gains to be made--any ideas? Is triple milling a thing?

 

[Gnomebrewer]

I crush at 0.037, and have gone as low as 0.025 without stuck sparges - 0.045 seems quite coarse. I can't see triple milling being of any use. If you can't get your LHBS to crush finer, and can't get yourself a grain mill, you could try mashing for longer (more time for the starch to be extracted) or accept the efficiency you're getting.

 

[doug293cz]

75% is not bad efficiency, and there is nothing wrong with just staying where you are. Your beer won't get any better if you improve your efficiency.

You could get a boost in conversion efficiency with a finer grind, but you will likely need your own mill to get there. A third pass thru a mill won't do much. Longer mash times should get you some increased conversion.

Brew on

 

[RM-MN]

Check what the difference in price might be if you bought grain in bulk and milled it yourself. You might be able to pay for a mill fairly quickly with the price difference. Corona mills are cheap and will do the job. Here's an example of the pricing.

http://www.discounttommy.com/p-189-...er-for-wheat-grains-or-use-as-a-nut-mill.aspx

 

[eric19312]

I'd get a roller mill. You have what sounds like a very nice system and if you get your own mill you will be able to take advantage of buying grain in bulk - cost savings - and brewing when opportunity arises instead of having to plan everything out a couple weeks in advance.

The corona mill is ok and there are ways to motorize but really you don't sound like you are going for cheapest solution with a recircing PID controlled brewery... Get a roller mill, and a low speed high torque drill. If you have the coin probably a monster mill or similar, else the various versions of the barley crusher work well too.

With a recircing system you may find a somewhat coarse crush works best. I found about 0.035-0.04 was better than finer. Probably on my system I get less channeling with the somewhat coarser crush and certainly less chance of stuck mash. Having your own mill will let you figure out what crush works best for your system and stick with that.

Next--whether you get your own mill or not you should probably consider mashing longer. This might also be crush related as I find even with recirculating mash I am usually not at 100% mash efficiency at 60 minutes. I guess it just takes longer for the moisture to mobilize the starch in the larger bits. Instead of iodine I have started using Braukaiser's table and a refractometer to check my conversion.

Table: http://www.braukaiser.com/wiki/images/3/3c/First_wort_gravity.gif
Full Article: http://www.braukaiser.com/wiki/index.php?title=Understanding_Efficiency

Basically the trick is to know your mash thickness you can look up your expected first wort gravity at 100% conversion. This is the gravity of the circulating wort in the mash after all starches have been mobilized and converted to sugars. Little tricky to use his table because he developed it for metric but easy enough to interpolate the values in Excel or just eyeball "close enough".

 

[Horseflesh]

Thanks for the thoughtful replies guys!

75% is pretty OK, but I am hoping to find some cheap and easy gains so that when I try making a very big beer the inevitable efficiency drop is alleviated.

I don't think my LHBS can adjust the mill per user, but I haven't asked yet. Their standard .045 is actually the gap recommended by my manufacturer, but it does seem like everyone doing E-BIAB with recirc recommends a finer crush anyway.

I've already calculated that milling my own would save me ~$2 for a typical batch from buying base grains in bulk. If I was able to improve my mash efficiency from 75% to 85%, which is supposed to be attainable on my system, that looks like another $1-2, depending on the recipe. But even though I love gadgets I am hoping to at least defer getting my own mill, if for no other reason than finding a place to put the gear and grains. However, a Corona mill like @RM-MN linked is cheap enough that it might be fun to play with anyway... I could grind my own without buying bulk to give it a try. Bookmarked!

That Braukaiser conversion efficiency table is super interesting, thanks for highlighting it @eric19312. Let's see if I understand this. Last night my mash thickness was 5.06 l/kg (2.43 qt/lb). Interpolating the table values, we get an expected maximum of 1.053.

But, here is a complication: my system has a giant dead space below the basket, about 4 gallons. (It's a 20 gal kettle but I am still only doing 5 gal batches.) My mash thickness is 2.43 qt/lb if you consider the total water volume, but if you look at just the water in the basket with the grain, the thickness is very different. Using last night's numbers:

8.62 gal water TOTAL, 14.22 lb grain --> 2.43 qt/lb, theoretical conversion maximum 1.053
4.62 gal water IN BASKET, 14.22 lb --> 1.30 qt/lb, theoretical conversion maximum about 1.093
(Mash pH was 5.3, btw.)

(The actual mash thickness was something a bit looser than 1.30 qt/lb because this is a pumped system, and the water level in the basket is typically about an inch higher than outside. The true value may be more in the neighborhood of 1.40 qt/lb and it will vary with pump speed. Then again, the grain bed settles and you get clear wort on top... Water and grain are not fully homogenized. More complications!)

I did not measure mash gravity, but after a half-gallon pour-over sparge and squeeze, my pre-boil numbers were on target at 1.052, and total mash efficiency was 75.8%. There is no way the mash SG was anywhere near 1.093 though. I tasted samples at all stages including the pH sample and I would have noticed. (Next time I brew I will be sure to calculate mash and lauter efficiency separately.)

So... assuming that the in-basket mash thickness is more meaningful for checking conversion efficiency, it seems fair to say that my conversion is not as good as it could be. This puts us back into talking about the crush and the mash duration as the next factors to tweak. Seem reasonable?

Whew. Thanks for reading if you are still here.

 

[doug293cz]

Thanks for the thoughtful replies guys!

75% is pretty OK, but I am hoping to find some cheap and easy gains so that when I try making a very big beer the inevitable efficiency drop is alleviated.

I don't think my LHBS can adjust the mill per user, but I haven't asked yet. Their standard .045 is actually the gap recommended by my manufacturer, but it does seem like everyone doing E-BIAB with recirc recommends a finer crush anyway.

I've already calculated that milling my own would save me ~$2 for a typical batch from buying base grains in bulk. If I was able to improve my mash efficiency from 75% to 85%, which is supposed to be attainable on my system, that looks like another $1-2, depending on the recipe. But even though I love gadgets I am hoping to at least defer getting my own mill, if for no other reason than finding a place to put the gear and grains. However, a Corona mill like @RM-MN linked is cheap enough that it might be fun to play with anyway... I could grind my own without buying bulk to give it a try. Bookmarked!

That Braukaiser conversion efficiency table is super interesting, thanks for highlighting it @eric19312. Let's see if I understand this. Last night my mash thickness was 5.06 l/kg (2.43 qt/lb). Interpolating the table values, we get an expected maximum of 1.053.

But, here is a complication: my system has a giant dead space below the basket, about 4 gallons. (It's a 20 gal kettle but I am still only doing 5 gal batches.) My mash thickness is 2.43 qt/lb if you consider the total water volume, but if you look at just the water in the basket with the grain, the thickness is very different. Using last night's numbers:

8.62 gal water TOTAL, 14.22 lb grain --> 2.43 qt/lb, theoretical conversion maximum 1.053
4.62 gal water IN BASKET, 14.22 lb --> 1.30 qt/lb, theoretical conversion maximum about 1.093
(Mash pH was 5.3, btw.)

(The actual mash thickness was something a bit looser than 1.30 qt/lb because this is a pumped system, and the water level in the basket is typically about an inch higher than outside. The true value may be more in the neighborhood of 1.40 qt/lb and it will vary with pump speed. Then again, the grain bed settles and you get clear wort on top... Water and grain are not fully homogenized. More complications!)

I did not measure mash gravity, but after a half-gallon pour-over sparge and squeeze, my pre-boil numbers were on target at 1.052, and total mash efficiency was 75.8%. There is no way the mash SG was anywhere near 1.093 though. I tasted samples at all stages including the pH sample and I would have noticed. (Next time I brew I will be sure to calculate mash and lauter efficiency separately.)

So... assuming that the in-basket mash thickness is more meaningful for checking conversion efficiency, it seems fair to say that my conversion is not as good as it could be. This puts us back into talking about the crush and the mash duration as the next factors to tweak. Seem reasonable?

Whew. Thanks for reading if you are still here.

For the Braukaiser method, it is the total water in the mashing system that counts. Doesn't matter if the water is under the basket or elsewhere in the plumbing. Since you recirculate, the wort will be homogeneous w.r.t. to dissolved extract concentration. (And, if the wort is not homogeneous, then the Braukaiser method gives inaccurate results.) I can explain further if necessary.

Brew on

 

[Horseflesh]

Thanks for the confirmation on that! I'll collect more data next brew day.

 

[btcost]

Iodine test will always be black with grain.

Clear wort only for the test. Best performed by placing a drop or two of clear liquid (wort) on a piece of large white chaulk.

Drop iodine into that. Check for color change.

 

[Horseflesh]

I've tested the wort many times and never detected starch so at least I am converting whatever starch is liberated.

 

[RM-MN]

Iodine test will always be black with grain.

Clear wort only for the test. Best performed by placing a drop or two of clear liquid (wort) on a piece of large white chaulk.

Drop iodine into that. Check for color change.

Only if you have starch left that didn't convert. My grains don't make any change in the iodine.

 

[doug293cz]

The only place you have unconverted starch is in the grits. Once a starch molecule gets dissolved into the wort, it very quickly gets cut into pieces too small to trigger a starch test. So, as others have mentioned, you are very unlikely to ever detect starch in clear wort.

A much better test than iodine is to quantitatively measure the amount of conversion by measuring the specific gravity of the wort in the mash. Method is here. This method doesn't tell you anything about the sugar profile (fermentabilty) of the wort, but neither does iodine. It will just let you know how much starch is still stuck in the grits. Any starch remaining in the grits is lost conversion efficiency.

Brew on

 

[btcost]

Only if you have starch left that didn't convert. My grains don't make any change in the iodine.

I️ don’t doubt you. However. I’ve done 120+ min decoction mashes. Hit 90+% efficiency

Brew house efficiency.

And every time I️ use iodine and there is so much as a kernel of grain present. The iodine turns black.

I️ don’t even use iodine anymore. I️ mash for at least 60min unless step or decoction. And am always 80% plus.

But yeah. Throw some iodine in the grains, and it tells me I’m not done converting.