Low ABV on the Chocolate Irish Stout
After much excitement building our own lautur mash tun and taking the plunge into all grain brewing, we measured a disappointing 2.021 FG and saw that our Chocolate Irish Stout only held 3.12% ABV.
Now, this really isn’t that far off the mark for an Irish stout, with Guinness at 4.2% ABV and Murphy’s at 4%, but we were hoping for a little more bite from our first lauter mash tun experiment. We added an extra 6 oz. of chocolate malt and a bit more Kent Goldings hops in the hopes of adding extra “fermantables” that the yeast could feed on.
POSSIBLE REASONS FOR THE LOW ABV
We did not maintain a consistent temperature during mashing, which could have affected yeast conversion. The recipe instructions had us partially mashing on the stove and then transferring to the mash tun only for the last few minutes; directions which are contrary to most mashing advice. As a result, the wort might not have converted enough sugar for the yeast to then consume (and thus less conversion to ethyl alcohol and lower ABV).
Still thinking about the mash, another culprit could be that our mash efficiency is low, perhaps caused by not grinding the grains up sufficiently. Using an online Efficiency Calculator tool, our ideal 100% mash efficiency is around 1.048 OG, and we measured 1.045, so not too far off the mark there. Another factor to consider is the yeast. This was our first bath using liquid yeast and we forgot to remove from the fridge and bring to room temperature for the full 1 hour recommended (what can I say, we drink home brew while home brewing and sometimes details are overlooked). Our pals at Listermann’s Supply think this might have been a factor in lower yeast activity. They also asked if we shook up the vial and I honestly cannot remember (again, I blame the home brew refreshment).
ONWARD WE BREW
Really, our first attempt at all-grain mashing didn’t turn out so bad. We have a few possible factors for the low ABV and a few ideas to keep in mind for next time. Some stouts do have a lower gravity and ABV, so we weren’t entirely off the mark there. An expected benefit might be that we can enjoy more of our low ABV home brew without getting a headache the next day …
about 5 months ago
I enjoyed the way you described your first experience with brewing the Stout. It is good that you can explain some issues you ran into and can offer readers ways to avoid your pit falls. Dwest gave me a book on home wine brewing so soon I hope to providing you information on my brewing experience.
about 5 months ago
That’s great! It’s a bit of an investment up front for the buckets and equipment but I’ve heard that brewing wine is easier than brewing beer. You could design your own label and share with friends, how cool would that be?
-Brett