About 3 weeks ago, I made a mild aleÂ that my local homebrew club is doing as a group brew. After I made the whole batch and was waiting for fermentation to start, I discovered that my thermometer was not properly calibrated. Instead of mashing at around 151Â°F, it probably mashed somewhere between 165 to 167Â°F. The activity in the airlock took off all the same, but then after about two days, things slowed down considerably. The beer had an OG of only 1.038 (being a low gravity mild ale) and after the first few days it had stopped at 1.020. I stirred the yeast up a bit, and it dropped to about 1.018 or so, but has not moved in about two weeks.
Since the beer has such a low starting gravity, it’s only about 50% attenuated, and is way too sweet. What happens when you mash at too high of a temperature is that the amylase enzymes that are supposed to convert the starches into sugars get de-activated by the heat. Thus the starches don’t get properly broken down into fermentable sugars. That’s about as much as I can tell you about what went wrong. If you’d like more information on this subject, check out John Palmer’s How To Brew website, where you can read all about enzymes, protein rests, dextrins and carbohydrates until your brain hurts. Biochemistry was never my strongest subject. I know that I usually heat my sparge water to 170Â°F, and when I dough in I get a mash temperature of about 152Â° or so. If you go to aÂ lower temp,Â your beer gets more fermentable and if it goes higher, it’s less fermentable.
So, what do I do with this overly sweet mild ale? Well, I don’t really want to dump it, so theÂ only option is to try to make it more fermentable and turn those long chain sugars into alcohol. Although it’s a bit controversial, the preferred method to do this is to add in Beano. This over the counter digestive aid contains alpha-galactosidase, which will break down the long chain unfermentable dextrins into fermentable sugars. The pitfall with this is that the Beano will keep working long after you’ve reached the gravity you want.
Last night I crushed up two Beano tablets and added them into the carboy. I’m going to rouse the yeast sediment every day or so and try to get the yeast to start fermenting whatever short-chain carbohydrates that Beano can pump out. When I reach an SG of about 1.010, I’m going to keg the beer and cool it, so that hopefully the yeast won’t keep on fermenting. I guess I could also add in a yeast inhibitor, but that would make it too much of a Frankenbrew. Stay tuned to hear what else happens with this one.