Brewing Lambic: Mythbusters Style

Lambic is the beer style who production is most plagued by myth, misinformation, and archaic procedures. However, the problem is that all of those unsubstantiated methods produce some of my favorite sour beers. After submitting an article about spontaneous fermentation in America to BYO for the July/August issue that was more of a “How To,” I thought it would be fun to make some bold statements about the evidence both against and in support of four things that everyone KNOWS about lambic.

1. Belgium (and the Senne Valley specifically) is the only place on Earth where the correct wild species of yeast and bacteria needed to ferment lambic live.

While it makes for nice marketing, this simply isn’t true. First there is the sensory analysis of the similar flavors produced in various spontaneously fermented American beers (Russian River Beatification, Jolly Pumpkin Lambicus Dexterius, and Cambridge Imperial Lambics). While I haven’t had one yet that is a dead ringer for a lambic, this is a type of beer that even in Belgium demands decades of practice brewing and blending to get right.

There was a study published earlier this month (Brewhouse-Resident Microbiota Are Responsible for Multi-Stage Fermentation of American Coolship Ale) that indicated that one brewery's American spontaneously fermented beer (specifically one brewed in New England using a coolship...) shares many of its fermentation characteristics with Belgian lambic. The authors used DNA analysis to show that many of the same key families, and even many of the same species (including Brettanomyces bruxellensis), are found in both. They also showed that the progressions of the two fermentations share strong similarities. There were subtle differences, but these may alternatively be a result of differences in process, or the length of time these microbes have had to ingrain themselves into the breweries.

2. A turbid mash of a grist including 30-40% raw wheat is the only wort production option for spontaneous fermentation.

While a turbid mash does extract starches into the wort, it is no more necessary for brewing a lambic than a decoction is for a Bohemian Pilsner. In Belgium, 30-40% unmalted wheat is part of the legal definition of the lambic/gueuze style, so that is a large part of why there is so little variation. Luckily, there is a beer like Cantillon Iris that proves a 100% malted barley wort can work equally well. While turbid mashes are employed at most of the best lambic wort producers, this may be a result of the fact that brewers who value traditional wort production are also the ones who value adequate aging time, and appreciate classic dry flavors.

This past Saturday I helped brew lambic at Dave and Becky Pyle’s house. If you don’t remember, I attended a blending session they hosted a couple years ago, and their lambic earned them NHC Brewer of the Year honors in 2005. Their wort production method doesn’t deviate far from a standard ale. This batch was half Pilsner malt and half malted wheat, mashed for 75 minutes in the low 150s F. There was no intensive near boiling sparge, and it was followed by a standard 60 minute boil.

3. A large quantity of aged hops is a requirement of the style.

The problem with aging hops to debitter them is that while their alpha acids are oxidizing into insoluble compounds, beta acids oxidize to become potent bittering compounds. The main role of hops in a spontaneous fermentation is to inhibit heat tolerant Lactobacillus that would lower the wort pH before the Saccharomyces can complete its initial fermentation. Most of the compounds that are anti-microbial are also bitter. Russian River uses around 25 IBUs of fresh hops in most of their standard sour beers with good results, this should be more than enough to inhibit even wild strains of Lacto.

While sour and bitter do clash, just a year of aging cuts the IBUs in half. By the time most spontaneously fermented beers are ready to be consumed, about two years after brewing, the IBUs in the wort will be below the flavor threshold even if you start around 30. However, the large quantity of aged hops may provide other compounds, glycosides, which can be stripped of their glucose molecule by certain strains of Brett and contribute unique aromatics.

4. You can’t start a spontaneous fermentation without a coolship.

Back to the Pyles. After the standard boil, with aged hops added at the start and mid-point, they run the wort through a plate chiller to drop the wort temperature to 68 F. From there it is pumped directly into the barrel (the water which had been hydrating the wood until a few minutes prior, remarkably had a pellicle). They started their house culture a decade ago with commercial pitches of the key microbes, but since then they have relied on the yeast and bacteria resident in the barrels, and from 750 ml of beer from one of their established barrels, to induce fermentation. The result is finished gueuze and kriek with an amazing, almost savory mushroom/loam aroma, along a sharply acidic lemon funk.

While Belgian lambic brewers do get some activity from the wild microbes that land on the wort as it slowly cools, so too does their house character develop from the reuse of barrels. In particular the air invites enteric bacteria, which produce a wide variety of funky fatty acids (along with alcohol and acid) that form the basis for some of the fruity esters formed by Brett over the months and years to come.

Big Boom?
The problem with experimenting with lambic production, and sour beers in general, is that the waiting time is so long. Most brewers, myself included, are hesitant to take a risk that saves a few hours on brew day if there is any chance it could detract from a finished beer that takes years to ferment and age. It is also hard to say how much the subtle effect of these shortcuts may cause because controlled research is basically impossible with spontaneous fermentation (even using identical processes and microbes the variation fermentor to fermentor can be gigantic).

My first spontaneously-fermented-turbid-mashed-aged-hop-infused-lambic should be ready to bottle in a month or two. I'm just waiting for the mulberries on the tree in my backyard to ripen, so that I can harvest them and rack half of the batch onto about two pounds per gallon. I just gave a small sample of the base beer to Claudio, who is going to see what microbes he can isolate from it. Look for a post about it on his blog, DC Yeast Lab (Plating DCambic).

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