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.
- 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.