Wild Brews: Beer Beyond the Influence of Brewer's Yeast

by jvetter 27. July 2008 17:15
I enjoyed this book very much. Both from a brewers perspective, but also in learning some of the science and history behind the Belgian styles that rely on bacteria. I read the book over my summer vacation at the beach in North Carolina, so it’s somewhat out of mind. If only I started the blog earlier, I would have the content fresh in my mind for review, but I don't so I'll do my best.

Classic Styles

The book mainly discusses a few styles of beers that come from the Belgian region that rely on native bacteria in the air and on fruit to aid in the fermentation of beer. These styles are:

  • West Flanders Red: reddish brown to deep burgundy in color. Ofter called the "Burgundies of Belgium," because of color and consistency. Some are fermented with a pure strain of brewer’s yeast and some with both yeast any bacteria. Typically aged in oak for 3 years, bottle conditioned, sweetened, and pasteurized. Tends to be much more tart and sour than the Flanders brown style.
  • East Flanders Brown:  redish brown to brown in color. Often referred to as an "Oud Bruin". Usually much more bitter that the reds though "mellowed by a malty sweetness". Typically fermented with a "mixed culture of yeast and bacteria and subsequently aged in stainless steel tanks at higher temperatures"
  • Traditional Lambic: pale yellow to deep golden in color. Often bitter with a lactic sourness, mellowing with age. Aged for 6 months to 3 years depending on what it is blended with
  • Gueuze: lambic made with 1, 2, and 3 year old lambic

Lambic

There are tons of interesting notes in this book on lambics, most important is understanding how these beers were traditionally made. Lambics are traditionally spontaneously fermented, which means they are purposely placed in a area that has decent amount of airflow from a nearby field or orchard. Typically the wort is placed in large cool ships in the highest part of the brewing building. A cool ship is essentially a long, wide, shallow vessel for holding beer. It's primary purpose being spreading out the beers so that as much surface area of beer comes in contact with the air. This enables the beer to cool quickly, but also provide inoculation with wild yeast and bacteria from the air. So the cool ship is generally considered to be the primary fermentation vessel for this style of beer.

There are several breweries that still spontaneously ferment there beers, but many will also add isolated strains of bacteria, or simply use a blend of isolated bacteria strains instead of spontaneously fermenting. Coolships and open fermentors can still be used in these cases, difference being better control over what goes into the beer for fermentation.
Fruit in lambic was and is often a common way of changing up a lambic to create a new and complex beer. Fruit is also a great source of bacteria and yeast because they live on the skins of the fruit. As a result the fruit was also a common source for the bacteria inoculation needed.

The Bugs

There are many types of bacteria and yeast that play a role in fermentation of beer, but the most commonly recognized are listed below:

  • Brettanomyces: Most important bacteria for wild beer production. Includes 5 recognized species, the most common being B. bruxellensis. Brett is a super attenuating yeast(near 100%), which means it can break down any type of sugar (simple or complex) if given enough time. This behavior "is attributed to, in part, the ability of beta-glucosidase inherent in Brettanomyces". More on that in a follow up post.
  • Lactobacillus: plays major role in the fermentation of flanders beers but a smaller role in lambic. It's claim to fame is that it can ferment in the presence of or lack of oxygen. It's primary bi-product is lactic acid. The most common species is L. delbrueckii.
  • Pediococcus: provides the majority of lactic acid found in lambic. Will ferment glucose into lactic acid without the CO2 by product produced by other bacteria.
  • Saacharomyces: Literally named "sugar fungus," is the primary source for brewing yeast. The S. cerevisiae is used in ale fermentation while S.pastorianus and S. uvarum are used as lager strains. Other strains such as S. globosus can often be naturally found in a lambic fermentation
  • Enterobactor: most notable for providing flavor compounds to young lambic (1-2 months). Only survive for a short period of time during fermentation because they cease to reproduce at a ph of 4.3. This is a good thing because in the same family of bacteria are E. coli, and E. Salmonella

 

Turbid Mashing

Lambics use a different kind of mashing method that does almost the opposite of what brewers today are doing with regard to sugar extraction from the grains. Typically brewers want highly fermentable wort which means mostly simple sugars (saccharides and disacharides) with few dextrins because they are not fermentable by standard brewer’s yeast. Lambic brewers on the other prefer wort with high concentrations of complex sugars (dextrins) because the highly attentuative brett used to ferment it produces more flavor and complexity in the resulting beer by breaking these complex sugars down.

It should also be noted that the history of turbid mashing actually stems from the tax situation in in the early 19th century. The beginnings of this mashing style date back to a 1822 dutch law that fixed a duty upon the capacity of the mash tun. To limit the impact of the duty, brewers created small mash tuns and filled them as full as possible with grain. As much liquid as possible was added and a lot of mixing was done. Liquid was continually drained off and later re-added with more water. The details of a turbid mash outside the scope of this post, but there is a good article describing it in the latest BYO. Essentially the result is wort with high concentrations of dextrins, which the bugs love.

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