Getting a head of beer


With winter winding down my thoughts turn to warmer times ahead when the cover comes off the grill and a cold beer hits the spot.  Last weekend my daughter and her husband motored down to New Ulm for Schell Brewery’s Bock Fest—a sure harbinger of Spring (and the desperation of home-bound Minnesotans). Increasingly I find myself turning to this next generation for keeping me on the bubble for brews.  For example, I now know that it’s helpful to carmelize freshly-tapped bock beer by poking it with a red-hot iron—preferably one laid among fiery logs until glowing hot. 

But never mind that, I want to pass along some results from another of this younger set, Tracy Lenz, on a more mundane aspect of drinking beer—achieving just the right head of foam on the pour.  For a graduate class in industrial engineering at Arizona State University (ASU) taught by DOE-guru Doug Montgomery, she used Design-Expert® software to experiment on foam height. A local microbrewer suggested that Tracy’s project team study keg pressure, temperature at keg and using Biofoam to make the brew more ‘sudsy’.  The team included two very different beers in the same experiment design, which turned out to be problematic for modeling, so let’s concentrate on one—an American red ale.*

It turns out that red ales foam readily so they need no encouragement with Biofoam.  Take a look at this response surface plot from the ASU study.  Figuring on 2 centimeters of foam as a good head puts the sweet spot (shaded green) at the no biofoam (-1) side with pressure needed to be set low (-1).  This result is achieved only if temperature is maintained at low level.

So there you go—a vital problem (especially for graduate-engineering students) solved.  Just one catch though—how you pour the beer into the glass may be the biggest factor for achieving a good head.  Here again the next generation comes to my rescue, for example last summer at an outdoor reception that featured a beer wagon with my favorite on tap: Lift Bridge Beer Company’s Farm Girl Saison ale.  My glass foamed over no matter how I positioned it under the tap.  It turns out that the trick is pouring along the side and then at just the right moment straightening up the glass while turning off the flow.  See what I mean via this Youtube video.  I found it easier just to stand by the beer wagon with an empty pint and a forlorn look until one of the younger fellows took pity on me.  Cheers!

*I learned from one of my sons that an ale ferments at the top, whereas a lager ferments at that bottom.  This is just one of many differences that are detailed by this beer-faq.

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