Brew day: Hoar Frost Oktoberfest

It's about that time again, so last week we brewed our Hoar Frost Oktoberfest. I recently bought a second burner so that I can easily do step mashes and decoctions, and for this brew I definitely wanted to do a decoction. However, I was also pressed for time, as I was taking my 3-year-old to his first Bears game later that evening. For those who don't know, decoctions involve removing a portion of the mash (the decoction mash) and boiling it before returning it the rest mash, and this can be a long process--especially if you're doing a traditional triple decoction. So this gave me a chance to think about decoctions and mash schedules and how to strike a balance between tradition and efficiency.

Hardly any American breweries employ decoctions (or even step mashes, for that matter) and many question if they're even necessary with today's highly-modified malts. In a perfect world, I'd love to brew side-by-side batches--one using a complex mash schedule, and one using a simple infusion--to really taste the difference. Unfortunately, there are so many other variables when brewing on a homebrew scale that even if I had the time to do this it would be hard to determine if perceived differences were due to the concoction or other things. Regardless, German brewers stubbornly continue to use step mashes and decoctions despite economic incentives to ditch the method, so I'll stubbornly continue to follow their lead.

Now, while I may be a traditionalist at heart, I'm still open to some concessions to efficiency. That generally means doing a double decoction instead of a triple one (this omits the acid rest, a rest done around 90°F to lower the pH of the mash, but these days you can easily manage mash pH with the addition of acid blend). My  understanding is that many German brewers these days go with a double decoction instead of a triple for that reason. However, if I want to further streamline my brew day, there are still plenty of questions about whether a protein rest is necessary these days, and if I ditch the protein rest and mash in at my sacc rest temperature, I can get away with a single decoction.

My awesome new cinder block brew stand.

However, one of the reasons step mashes and decoctions get malt complexity is because they move back and forth through different beta- and alpha-amylase ranges, and if I just mashed in at, say, 152°F and then did a decoction up to a mash-out temp, you'd lose all that. I figure you might as well just do an infusion mash then (especially since I rarely mash out anyway).

But reading Darryl Richman's Classic Beer Style series book, Bock, I noted that German brewers would use a lower rest temperature for the thinner rest mash and then use a higher rest temperature for the decoction. That way you're moving through the beta- and alpha-amylase ranges in your decoction to get some nice malt complexity (along with the Maillard reactions that come with the decoction itself), but you're really only adding about 45 minutes to your brew day. It's essentially the double decoction employed by many German brewers, but it omits the protein rest.

So, short story long, that's what I ended up doing. I did a fairly thin mash at 2 quarts per gallon and mashed in at 147°F. I then pulled a relatively thick 18-qt. decoction mash and raised it to 158°F. I held it there for 20 minutes and then boiled it for 15 minutes. I added it back to the rest mash over a five-minute period, which ended up actually overshooting my 168°F target for mash-out by about four degrees. Some vigorous stirring got the temp back under 170° fairly quickly.

After collecting my 12.5 gallons of wort, I did a 90-minute boil with hop additions at 90, 60 and 45 minutes. I added Irish moss at 15 minutes. After chilling, I collected about 11 gallons and was shocked to find my O.G. at 1063. My target was 1056. 84% efficiency? I'll take it. Anyway, I threw the carboys in the chest freezer overnight to bring them temp down around 48°F and aerated and pitched the next morning. On a side note, I pitched a slurry that I collected from my Schwarzbier. It's my first experience with yeast-washing and it seemed to work well. The next day it was fermenting like crazy!

Oh, one last thing I should note... When I'm bringing the wort to a boil, I usually throw a probe digital thermometer in there and set the alarm to go off around 210°F so I can make sure to pay close attention and avoid boil-over. Much to my dismay, my thermometer read around 215°F when it finally came to a boil. I'm really hoping that doesn't mean I was off three degrees on my mash temps. So let this be a lesson to everybody... calibrate your instruments regularly! Hopefully my beer won't turn out too thin, but if it does I suppose I'll know why.