On the first Saturday of Beer Week, the Press Club offered a flight of the Mikkeller Yeast Series. Mikkeller, a Danish beer maker, took a Pale Ale wort and fermented it six different ways with a Saison, English, Lager, American, Brettanomyces Bruxellensis, and Brettanomyces Lambicus style yeasts to about 6.5% abv. The beers were riveting for their similarities, their differences and, in reflecting upon them, for the ways that they mirrored the best attributes of SF Beer Week.

Yeast, the single-celled organism most well know for producing the alcohol in beer, also plays a significant though often less noticed role in the aroma, flavor and mouthfeel of beer.

All of the beers had the same warm burnt orange color but the first four (Saison, English, Lager and American) ranged in clarity from slightly hazy to very cloudy, where as the two Brettanomyces beers were completely clear which allowed the light to dance through them like a fine Cognac. The differences in clarity was the first indication of the dramatic impact of yeast on beer. Because while the color of beer is dependent on the different types of malt used, the clarity of the beer is dependent, in part, on yeasts ability to acts as a flocculating agent (pulling particles out of suspension).

In a similar way, each yeast strain uniquely affected the aroma, flavor and mouthfeel of the beer. The Saison beer had a rich bready aroma with the pleasant earthy notes of a damp forest. However, the flavor was bright and citrusy with notes of grapefruit and orange pith (the white flesh on the inside of citrus fruits). The beer had tiny bubbles that exploded on the tongue creating a tingling sensation.

The English beer had a strong aroma of fresh hops and tasted of orange zest, Campari, and a lingering bitter finish. The English beer had a smooth almost creamy texture common to English style ales that was a pleasant contrast to the bright citrus and bitter flavors. The Lager beer's aroma and flavor had the same hop and citrus character as the English style but both were less intense. The aroma had a rounder and more subdued quality while the flavor tasted flat and one dimensional.

The American beer, had a well balanced aroma with a top note of hops and lower note of baked bread. Similarly, the flavor was balanced between sweet and citrusy and it had a pleasant finish. The beer was medium bodied with a nice amount of carbonation that prevented the sweetness from dominating

The two Brettanomyces beers were fascinating. The Brett. Bruxellensis beer had a strong funky aroma that was smelled slightly of sulfur and vinegar but in a strangely pleasant way. In contrast it tasted fresh and sweet and it had a clean mineral finish. In concert with its glass like clarity it felt smooth and light on the tongue. The Brett. Lambicus was completely different. The initial aroma smelled slightly woody and had a strong alcohol note, but as it warmed up, it smelled almost of pot roast, that was simultaneously meaty and vegetal.

While all the beers were interesting, the American style yeast presented the the most well balanced beer of the series. Simultaneously I felt surprised and silly for questioning whether an American style yeast would be the best match for an American style pale ale. In this way Mikkeller's Yeast Series proved to be a microcosm for Beer Week as a whole.

San Francisco Beer Week presents the best attributes of craft brewing, its creativity and its dogged pursuit to make the best examples of traditional beer styles. The beers of Mikkeller's Yeast Series lives up to this completely. Five of the beers were creative examples of how to re-imagine a classic style with interesting results that were both tasty and educational. At the same time, the American beer in the series demonstrated that the traditional combinations of grain, hops and yeast are classics for a reason. This mix of creativity and traditionalism (in the best sense of the word) could be found at almost every event of Beer Week. This winning combination helps to explain the continuing success of Beer Week and why there are over 2,000 craft breweries in the United States, with more being added every year.