Comparing Apples to Oranges Part 2 of Aerated steeping vs. Un-aerated steeping

11 Aug

After brewing with my aerated malt and the un-aerated malt I’ve come to realize that there is a major flaw with this comparison. So much so that I had decided not to post the results until I redid this experiment. Then I received some enthusiastic words of encouragement from some readers who were waiting for these results, thanks, Arman and Graham! I did learn something while doing this so I think it is worth posting but keep in mind this will be the first of many comparisons of aerated an un-aerated malt. Here’s part 1

The main flaw with this experiment was basically how the low germination temperature adversely affected the aerated malt. Both batches were malted at the same time at the same low temperatures; 5-10C for steeping and 10-12C for germination. I believe it was because of this that the aerated malt did not have the diastatic power that it would have if malted at a higher temperature.

Malting the aerated barley at the same temperature as the un-aerated did prove that it was the un-aerated steep that delayed the growth, or that aeration speeds up growth, but in order for the faster growing aerated malt to develop enough enzymes in its short germination period it needs warmer temperatures in the 15-18C 59-64F range and not the 7-12C 45-54F range. According to Briggs “Steep aeration reduces alcohol production and often leads to subsequent more vigorous germination and  respiration during the germination phase.” (pg 209) Visually the roots were not as long as I normally see them (as expected due to the cold temperatures) but the acrospires seemed long enough and the starch was pasty so I was duped into thinking it was modified when it really wasn’t.

When making the beer I had to mash the aerated malt for 3 hours and it still hadn’t fully converted (using an iodine test). The un-aerated took 1 1/2 hours to fully convert. These were small 2 gallon batches, the recipes were the same, fermentation temperatures were the same but they were brewed on different days.

Aerated :

  • O.G. 1.057
  • F.G. 1.009 6.14% abv.


  • O.G. 1.061
  • F.G. 1.0055 7.3% abv.

Another tell tale sign of under-modification in the aerated malt was a stuck sparge. So not only did I have to decoct this mash a couple of times to maintain the temperature but I had to transfer the whole thing to a large strainer and batch sparge it. Hands down, this was my most disappointing brew day ever. The un-aerated ended up producing more wort at a higher gravity.

Since one malt was under-modified and the other was not it is not really a good comparison. I should be comparing a really well-made example of an aerated malt germinated at a higher temperature that is well modified to a good example of a traditional un-aerated malt germinated at a cooler temperature, which is what I plan to do next. You might be thinking, why not germinate the un-aerated malt at the same higher temperature as a modern malt? With un-aerated malt, higher temperatures may cause uneven germination. According to Briggs (209) ” …at these (16-18C) and especially higher temperatures water sensitivity (dormancy) will be induced and the grain will germinate unevenly. To some extent the adverse effects of higher temperatures may be offset by the use of air rest during steeping”

So what I learned is that aerated malt is a different animal (more vigorous) with different needs (higher germination temperatures) than un-aerated malt.

Taste test: In a nutshell, the un-aerated had a richer maltier flavour but lacked body, the aerated had more body less flavour. Again the brewing of these two beers was so varied that it’s not a good representation of the malts characteristics. What we have is a very well modified malt and an under-modified malt. One theory as to why an un-aerated steep produces a more well-modified malt is that not only is it given more time to develop but that the endosperm is more fully saturated. (See Briggs, Malts and Malting pg 95-96) During an aerated steep the barley often chits even before the steeping is over. When the grain chits, water is absorbed through the embryo faster, so the grain may reach the target steep weight but the endosperm may not be as consistently saturated as a grain that does not chit during the steep. This may also make germination more consistent with the un-aerated malt. The pictures show these traits quite well. The aerated malt is more cloudy and has more head whereas the un-aerated is clear and loses

The pictures show the modification traits quite well. The aerated malt is more cloudy and has more head whereas the un-aerated is clear and loses it’s head quickly. I’m really looking forward to trying this experiment again and I’ll also compare it with store bought malt.


After tasting Aerated on left, un-aerated on right

Aerated malt beer on left Un-aerated on right


Posted by on August 11, 2017 in un-aerated malt



12 responses to “Comparing Apples to Oranges Part 2 of Aerated steeping vs. Un-aerated steeping

  1. Demy

    August 11, 2017 at 8:37 am

    This is really a great post, my compliments! I have some considerations: from my tests the very high germination temperature (germination in summer) is negative for both types of malt, most in non-aerated malt. Low areated malt had a long but very regular germination and the malt flavor was very intense so basically I agree with you. In beers that you’ve produced the differences may be due to a long mash, for example greater protein abatement and greater gelatinization / conversion (so clearer and greater OG) do you think it’s possible? By the way, I read that the enzymes (not considering temperature) are denatured, however, arrived at 2 hours of mash is correct or there is no time limit? If it may be interesting I have had very long mash (and partial conversion) with barely fresh malt but still good efficiency, that’s why I think mash long free somehow more starch / sugar from the grains.

    • jfdyment

      August 11, 2017 at 3:50 pm

      Hi Demy, yes, originally I wanted to make the two beers with exactly the same mash times but I had decided to extend the mash time of the aerated beer because after an hour it was nowhere near being converted and I realized that it was very undermodified. I had sort of suspected this before brewing with it, anyway it was at that point I that I had to admit that the experiment was flawed because of this and I was dealing with two different malts. By the way it was the aerated malt that had the long mash that turned out hazy and with a lower O.G. I haven’t heard of long mashes denaturing enzymes, I’ll look into that. When a malt a long mash I usually monitor it’s progress with iodine tests every hour or 1/2 hour and I usually keep mashing until conversion looks complete or at least close to complete.

      • Demy

        August 11, 2017 at 8:20 pm

        Thanks a lot for the answer, I read wrong! However, one thing is certain: 1) for good malt the germination temperature (barley) must be fresh. I have experienced very low germination temperatures (even 28 ° C, summer cause) and the result is not a homogenous germination, a part that does not germinate at all, resulting in sucrose problems (I think the production of enzymes is poor). 2) A break after germinated barley can make a difference. When I turned without air, the temperature was low and the germination was very homogeneous, I was very impressed and during the mash I had a very fast conversion. Say this to compare our experiences and I think many things fit. By the way, I did the acid tree using sauergut as input: the result is a much more powerful malt than the previous procedure (tasting is really a sour but pleasant burn) I recommend trying. (For experiment, after did the saccharification to get the crystal malt caramel/acid) to test new horizons !! Thanks again for your patience

      • jfdyment

        August 12, 2017 at 5:41 am

        Hey Demy, how did your oat malt turn out? My oat beer tastes like green corn husks, it’s rather nasty.

  2. Christopher

    August 11, 2017 at 1:41 pm

    Great work, Francois! The need for germination temperatures is really interesting, and the visual differences in the beers are a cool demonstration of the ideas.

    • jfdyment

      August 11, 2017 at 3:35 pm

      Thanks Chris! How’s the harvesting going? The spreadsheets are looking great, love the pictures!

      • Christopher

        August 12, 2017 at 5:31 pm

        It’s all out of the field, and we’re about 1/2 done cutting seed heads. We should have a bit over 100 lbs from 20 varieties, and then all of the other year 1 stuff. We’ve started getting varieties back from Harlan members, which has been really exciting!

  3. Demy

    August 12, 2017 at 7:49 pm

    Hey François, my oat malt was treated like pilsener malt, I did not use it for 100%, but only the addition (15% in oattmeall stout) and a beer with corn + oats (for my sister Who suffers from celiac disease 28%), I used it with corn because oats have the skin that helps during filtration (I did not read it anywhere, it was my experiment, because only wheat is difficult to filter ). The strong beer was unfortunately infected (I think it was Candida Mycoderma) but wheat corn beer was very good.

    • jfdyment

      August 12, 2017 at 10:45 pm

      That’s too bad, I’m just starting a hulled oat malt to avoid the husk flavour, I’ll make a post about it soon.

      • Demy

        August 13, 2017 at 6:15 pm

        Fantastic. About peel, I know there is a roasted malt without peel … (in Italy it could be done with “pearl” barley, at least I think) but I’m experiencing another road using wheat instead of barley (like roast barley, without germination ) That has no peel. It’s already done but I have to try it in a beer again.

  4. Arman

    August 22, 2017 at 7:51 am

    Hey Francois, Great update! I decided to do my own experiment a week ago along the same lines, except that both aerated and unaerated batches would be kept at the same low temperature (~7C). Both batches had a water content of ~43-44%. The water temperature was similarly low during the steep, ~7C. I achieved a water content of ~43% on day 2 with the aerated barley, and on day 3 with the unaerated barley. The aerated barley started chitting two days ago (day 6), the unaerated barley is now chitting (day 8). I found that the unaerated barley started drying out quite a bit when I checked on day 6, I had to cover it with a damp paper towel. From the ways things are going, this could be a three week germination. Seems extremely slow.

    • jfdyment

      August 22, 2017 at 2:59 pm

      That is very slow, probably due to the temperature. I might not have made it clear in this update but both of my batches were also at the same temperature around 10C for steeping and 12C for germination. The point I was trying to make was that at a low temperature your aerated malt might not have the diastatic power you would get at temperatures around 15C even though it may appear to be modified (long acrospires etc). Let me know how things turn out. Francois


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