Eye of the beerholder

Last year, I brewed a beer at home with the plan of giving bottles of it to friends and family for Christmas. It was a strong IPA, with a target alcohol content of about 7 percent. I had made an IPA the previous spring with excellent results. So, I repeated the recipe, but this time, something went wrong—sort of. The IPA tasted like butterscotch by the time it was ready to be bottled.

I know what some of you may be thinking: Butterscotch is one of the finest flavors known to man, surpassed in excellence only by white truffles of Alba and the fatty belly meat of a fresh king salmon. So, in what way had something gone wrong?

Well, here’s the funny thing: In the world of making and appreciating beer, that wonderful, thick and chewy flavor of butterscotch is a qualitative flaw. Butterscotch is bad. The flavor comes from a molecule called diacetyl (pronounced by many as “die-ass-it-ehl”), which is usually created in a beer by the yeasts that ferment sugar into alcohol. Fermented at the appropriate temperature, yeast will produce an insignificant and tasteless amount of diacetyl. Fermented too warm, though, and diacetyl may overtake a beer.

While it can appeal to many taste buds, diacetyl generally should not be in a beer.

“In some beer styles, a little is OK,” says Damien Perry, the president of the Marin Society of Homebrewers. “It’s what gives nice butterscotch flavors to a lot of English beers.”

Barleywines and Scotch-style ales, for instance, can benefit from a touch of diacetyl. In an IPA, though, it’s not what you want. I kept quiet about the fermentation goof, and I handed out bottles on Christmas morning anyway.

“It’s nice; it tastes like candy,” my brother-in-law told me shortly after New Year’s.

I cringed but accepted the praise.

So, why is something that tastes good considered a flaw in beer?

“It’s probably just based on historical norms,” Perry says. He means that most beer styles have been made for decades or centuries, and each style has its standardized flavor profile. Butterscotch just doesn’t fall into that profile in most cases.

In fact, diacetyl truly can taste terrible at times. I have tasted white wines that seemed like they’d been spiked with vanilla extract, so potent was the diacetyl flavor. My Christmas IPA, too, developed an even stronger butterscotch flavor over the course of a couple of months. By March, the last remaining bottles were cloyingly bad.

There are other flavors that both plague and pleasure the makers of beer and wine. Brettanomyces is a genus of yeast that creates a flavor usually likened to horse blanket or barnyard—and most winemakers fear Brett, as they call it, like the devil. On the other hand, Brett beers have become a wildly popular category, with brewers intentionally infecting their beers with the funk-producing yeast.

Acetic acid—which makes vinegar taste like, well, vinegar—is another loved and hated compound among craft beverage makers. Whereas acetic flavors may indicate that a wine, beer or cider is over the hill, just a touch can be lovely. The ciders of northern Spain are tart with the influence of acetic acid, and they are among my favorite things to drink.

Perry says that sometimes the essence of banana will develop in a beer. This, he says, is “undesirable in most styles but perfectly acceptable in a hefeweizen.”

Beer flaws are a subjective matter. While formal brewing instructions and beer judging guidelines serve the purpose of at least reminding us what a beer should taste like—and what a given style has traditionally tasted like—if you like the taste of vinegar or barnyard, a “bad” beer might be a good one.

In fact, according to my family, my Christmas IPA was the best beer I’ve brewed.