It was pretty much a regular birthday for me. It will likely stay in my friends' minds more than mine. My friend and business partner brought a rare bottle of beer: Lost Abbey Veritas VII. It was a beer that I tasted a few months back. I was blown away. When we opened the bottle this time, we offered sips to our friends. Here are some of the replies: “What is this stuff? It's crazy!” “It tastes like vinegar! Yet in a strangely good way!” “This is beer???!! Really?” Surrounded by people with varied and acute palates, here was something wildly new to them. Everyone wanted to know what this beer was and how it was made. Why is it so different from other beers? Why does it taste like vinegar? Why does it taste like raspberries?

Stylistic discussions aside, most beers are a careful and concerted interplay between sweet grainy elements (stemming from the malt in the brewing process) and some sort of bitterness (which usually comes from hops but could fundamentally come from anything). The unsung hero of the brewing process is the yeast; yeast is what allows these elements to come together. Brewers are a careful bunch. They only introduce certain yeasts at certain times. This allows the final product to be consistent from batch to batch. So what happens if you leave the proto-beer out for wild airborne yeasts to land? What would happen in this microbial freeforall? Sour beer.

Sour beer is perhaps the final frontier. Almost every other beer is a complex meditation and dance between the malt and the hops. The yeast of course contributes a flavor, to be sure, but generally, their most important function is to feast on the sugar in the malt, creating alcohol and carbon dioxide as its byproducts. Sour beers, however, don't just showcase these yeasts: they cherish them.

Without delving too deeply into arcane and esoteric chemistry, yeasts eat sugar. They emit carbon dioxide and alcohol as byproducts. This is what turns that unfinished wort (the name for the malted barley steeped in hot water, which smells sort of like long-stewed oatmeal) into a sort of proto-beer. Years ago though, certain brewers opted against manually introducing yeast cultures into the mash; instead they just left it out and let the local airborne flora land in the wort and do their work. Some of the yeast that settled did just that: turning sugars into alcohol. These yeasts, various types of Saccharomyces, nicknamed “brewers yeast” does just this: converting sugar into alcohol and imparting a light and clean flavor. But other yeasts land there as well. These yeasts, well, these yeasts are FUNKY. And they impart extremely distinct flavors into the beer.

We've come full circle. Hundreds of years ago, souring yeasts landed in the beer wort by accident. Today many American brewers embrace these flavors and intentionally introduce these sour-producing yeasts. And I'm not talking about a kind of “citric” lemony sour. I mean sour. Beers that taste like balsamic or apple cider vinegar. In fact, some of the byproducts of these souring yeasts are: acetic acid — the chief component of all vinegars; malic acid — the acid you'll find in apple seeds (the beer posseses elements akin to a cider); even butyric acid — what you get when butter goes bad — the best way to describe it is a quasipleasurable rancidity. The main yeasts responsible for these flavors are Brettanomyces, Pediococcus, Lactobacillus and Acetobacter. Of the four, it is the Brettanomyces that are responsible for most of the “funk” on these beers. When you try one of these beers and you start thinking of words like “barnyard-y” or “sweat sock-ish” or “horse blanket-esque” — that's the Brettanomyces or “Brett.”

I know, I know, it sounds really weird, but these are some of the most interesting beers out there. These complex aromatics are unlike anything else. More akin to aged champagne than any other beer on the market. They are light but earthy. Beautiful microcarbonation which lifts food delicately off the palate. And they age! Most of these beers actually become better over time: the sourness fades leaving behind subtleties that were otherwise occluded.

Here is a(n extremely partial) list of a few American breweries that produce one or more varieties of sour ales: Russian River Brewing – Temptation, Supplication, Consecration (and a host of other “Tion” beers); Jolly Pumpkin – Oro de Calabaza, La Roja, Calabaza Blanca, Maracaibo Especial; Lost Abbey – Red Poppy, Cuvee de Tomme; The Bruery – Oude Tart. And here are a couple Belgian breweries that have been making sour beers for a while: Rodenbach, Regular or Grand Cru; and Duchesse de Bourgogne

Jason Bernstein is the co-owner of Golden State.

LA Weekly