Why Does My Beer Taste of Butter?
Diacetyl (die-ASS-uh-teel), or 2,3-butanedione, is a flavor found in some beers. Maybe you’ve heard beer nerds talking about it in their secret code: “butter bomb” or “the big D.” When a beer drinker is offended by diacetyl he or she may reluctantly choke it down or even refuse it altogether. It leaves a bad taste in the mouth, figuratively and literally.
Tiny amounts of diacetyl in beer can lend a butterscotch-like flavor and a caramel complexity. English and Scottish ales sometimes exhibit it, as do some Czech pilsners. Chardonnays may have noticeable diacetyl, too. How could this be a bad thing? Who doesn’t like a little butter or butterscotch?
Exceeding trace amounts can cause a beer to be dominated by a chemically, greasy, mouth-coating, popcorn butter flavor that ruins the beer drinking experience altogether. And once you know what it smells like, you may become disinclined from even taking a sip.
Strangely, not all beer drinkers are offended by this taint. Human individuals have a varying taste threshold. Furthermore, some people who have become accustomed to diacetyl as a house character appear to actually like it. Is this because they indeed prefer it, they aren’t bothered by it, or because they don’t even notice it?
It’s the Yeast… errr… the Brewer
Shortcuts are fine when they lower cost or increase consumer choice, but not when they affect product quality. Perhaps diacetyl is held in such disregard because the two major causes of it have to do with brewers and bar owners taking shortcuts. In this article we’ll focus on brewing methods that promote diacetyl. In a subsequent piece we’ll touch on dirty tap lines and infected beer.
All beer yeasts produce some diacetyl early during the fermentation. In later stages of fermentation, healthy yeast consume the free diacetyl unless the brewer has chilled the young beer too early. Crashing, as it is called, is a technique to promote sedimentation of proteins and yeast in the beer by chilling to near freezing. If the beer is crashed too soon and then served, the diacetyl will remain.
Beers are prone to diacetyl when fermented with the famed Ringwood yeast, or Bohemian lager strains, and they are crashed too early. When using these strains, the brewer must allow beer that has been cold conditioning to warm up to the 60s for a day or two in order to promote the metabolism of the remaining diacetyl. This is called a diacetyl rest. The diacetyl rest takes time and consumes more refrigeration energy, because the beer has to be chilled twice.
It didn’t help that the early proponents of brewing with Ringwood yeast advertised the ability to produce “beer in five days.” By fermenting the beer very fast and getting it transferred to your serving tanks or bottling line, you need less tank capacity and you pay for less refrigeration in your brewery. Great if you’re an accountant, but not so good if your customer base abhors diacetyl.
Englishman and biochemist Alan Pugsley takes the credit for bringing the Ringwood method to the US. The “method” includes not only the proprietary yeast strain, but also the use of open fermenters and the principle of top cropping to harvest yeast.
Pugsley, like diacetyl, is not without controversy. As beer writer Andy Crouch tells it, Pugsley comes across as indignant towards the wave of Ringwood critics while being commensurately critical about strong or exceedingly hoppy beers.
As a consultant on brewery startups, Pugsley has influenced many breweries, including: Magic Hat, St. Ambroise (now called Brasserie McAuslan), and Middle Ages Brewing Co. Middle Ages’ brewer Marc Rubenstein interned at Shipyard prior to opening his Syracuse brewery with his wife Mary.
While each of these breweries has gone on record about how they deal with diacetyl production, there is no doubt to this writer that the beers they produce still contain it. The levels can vary between recipe and batch, from marginal to intolerable. In some beers, a touch of diacetyl adds some complexity. But when diacetyl dominates the flavor and mouthfeel of a beer, I, for one, will send it right back. TPJ
Ed. Thanks to regular reader BR for suggesting this topic. Requests are always considered.