When it comes to bacteria, most reach for the hand sanitizer or run in the other direction from the “germs.” That’s no different in the beer industry, where these organisms cause spoilage and unwanted flavors including butter and vinegar. Breweries will do everything possible to avoid potential beer infections ... except when the brewer desires the sour and tart outcomes that only certain bacterial strains can create.
While there are plenty of harmful bacteria species that wreak havoc on the human immune system, none of these bad, pathogenic bacterium have ever been associated with beer, according to author Fergus Priest. Because beer has ethanol, a low pH (high in acidity), no significant nutrients (sorry), and lacks oxygen, it is far from an ideal environment to host bacteria. Add hops, which have anti-microbial compounds, and you have an even less hospitable environment. Only a few strains can survive this ecological niche and they include: acetic acid bacteria (think vinegar), lactic acid bacteria, Obesumbacterium, Pediococcus, Pectinatus and Zymomonas.
Many of the great sour beers from Belgium, Germany, and now America, rely on Lactobacillus and Pediococcus, (often in unison with the wild yeast Brettanomyces). In Belgium, Flemish Brown and Red Ales acquire the “bugs” from oak barrels, or at another stage of inoculation. In the case of Lambics, open or “spontaneous” fermentation adds tart characteristics due to the presence of these amazing airborne critters. The German Gose and Berliner Weisse — while very different sours — also attain tart and funky traits from the use of such wild bacteria and yeast. American brewers have acquired an insatiable taste for these brews of late, and the trend appears to be growing as more people demand a tart and dry, yet refreshing flavor profile.
One souring method now very popular with U.S. brewers is known as “kettle souring.” The process allows brewers to create a sour beer in just a few weeks as opposed to the amount of time it would take for a Lambic or Flemish Ale. The technique also cuts down on cross-contamination risks because souring occurs in the boil kettle where bacteria are killed before wort is transferred to the fermenter. For a nice example of this style seek out a can of Two Roads “Zero to Sixty” Tart IPA. This kettle-soured brew is not only a unique take on the IPA, it proves that the good or bad nature of bacteria sometimes depends on the beer-holder.
This week’s recommendation: Two Roads “Zero 2 Sixty” Tart IPA hopped with Comet and Chinook and then kettle-soured for a tart finish. 6% ABV. Stratford, CT
— Colin Hubbell is co-owner of the Green Onion Pub and the Hop and Goblet in South Utica, New York.