Brewing with Brettanomyces Yeast Cultures and Lactic Acid Bacteria
Brewing beer with wild yeast and bacteria adds a new level of complexity to an already complex process. Making beer with these specialty cultures is less precise and much less predictable than brewing with a single yeast strain. The rewards however can be tremendous if a brewer has patience.
The most important factor to keep in mind is that these cultures take time to fully develop and do their jobs. A good lambic or sour style beer usually takes 1 to 2 years to fully develop. The temperature at which the beer is fermented and then stored will play a large role in determining how quickly the characteristic aromas, flavors and acidity develop.
Growing and Managing Wild Yeast and Bacteria
Saccharomyces cerevisiae and Saccharomyces carlsbergensis are, in many modern brewers’ minds, the only desirable microorganisms in the brewing process. For the vast majority of beer styles, this is true. There are, however, a few styles of beer that require what are considered spoilage organisms to create the desired profile.
In the traditional setting nature acts as the source of the desired cultures. Cool ships and fermenters that are open to the air allow a host of microbes to enter the wort. It is the specific combination of these microbes and their sequence of activity in the fermentation that creates the unique and complex profile of lambic and sour beers.
The following is a list of the cultures involved in true lambic fermentations and the sequence of activity:
- Enteric bacteria (3 to 7 days)
- Kloeckera apiculata (3 to 7 days)
- Saccharomyces species (2 weeks)
- Lactic acid bacteria (3 to 4 months)
- Brettanomyces yeast (8 months)
- Oxidative yeasts (8 months)
Each one of these groups of organisms adds some character to the finished beer; however three groups in particular do the lion’s share of the fermentation and contribute the bulk of the flavor characteristics. Typically, it is impractical to try and manage all of these cultures. The enteric bacteria and the Kloeckera apiculata are not readily available and contribute the least amount of character to the final beer. The Oxidative yeasts are also not readily available and also contribute very little to the final profile of the beer. That leaves the Saccharomyces yeast, the lactic acid bacteria, and the Brettanomyces yeast.
The bulk of the available sugars in the wort are fermented by a Saccharomyces strain. In modern lambic brewing, the rate at which fermentation begins is much quicker than in a traditional lambic. The brewer has a large number of choices on how to begin the fermentation. The easiest choice is to use a prepared lambic culture that contains the Saccharomyces culture along with the lactic acid and Brettanomyces cultures. The other choice is to use any other commercially available Saccharomyces culture. If the prepared lambic culture (Wyeast 3278) is used, it is important to keep the primary fermentation temperature relatively low (68-72°F) in order to keep the lactic acid cultures in check. If the temperatures get too high, the bloom of the lactic acid cultures can inhibit the Saccharomyces cultures.
If the brewer chooses not to use a prepared lambic culture, then any Saccharomyces culture can be used for primary fermentation. The primary fermentation should be allowed to progress for about two weeks before adding the lactic acid cultures. This allows plenty of time for the primary culture to establish itself and complete the bulk of the fermentation.
When the main fermentation is complete and the Saccharomyces population in suspension begins to decrease, the lactic acid bacteria start to increase in population. If a prepared lambic culture was not used, this is the time to add the lactic acid bacteria. It is important to note that Lactic Acid Bacteria is very sensitive to even moderate levels of IBU. Keep IBU levels below 10. The lactic acid cultures responsible for souring a lambic beer are: Pediococcus and Lactobacillus (Wyeast 5733 and 5335 respectively). The temperature of the fermentation should be allowed to rise to allow the lactic acid cultures to establish themselves. The sourness will continue to increase for up to 2 years.
The final players in the homebrewed version of a lambic beer are the Brettanomyces yeast. The available cultures are Brettanomyces bruxellensis and Brettanomyces lambicus (Wyeast 5112 and 5526 respectively). If a prepared lambic culture has not been used, the Brettanomyces cultures can be added anytime after primary fermentation is complete. The Brettanomyces cultures are slow growers that are able to ferment complex sugars that Saccharomyces is not able to utilize. These cultures do not add a significant amount of alcohol to the beer, but they are the primary contributors to the aroma of the finished beer. The characteristic horsey aroma and flavor are by-products of Brettanomyces metabolism. These cultures also produce large amounts of ethyl lactate and ethyl acetate along with some acetic acid. These cultures can remain active for 16 months.
For the home brewer, the prepared lambic culture is the best choice for producing a great lambic beer. The cultures contained in the lambic blend will perform their jobs in sequence as long as the primary fermentation temperature is kept under control. If a brewer is looking to make a Berliner weisse or a sour brown, then the lactic acid cultures should be added with the pitching yeast in primary fermentation. Once again, it is important to keep IBU levels below 10.
The lactic acid cultures and the Brettanomyces cultures are both slow growing cultures that have complex nutritional requirements which makes growing and maintaining the cultures problematic. It is extremely important that brewers using these cultures understand that the beer will take 1 to 2 years to develop the desired characteristics.
Berliner weisse brewing techniques are similar to most German brewing techniques. The main difference is decoction mashing is not used to achieve the temperature steps in the mash. Modern Berliner weisse breweries now use multiple step infusion mashes. None of the brewing techniques for this brew are necessarily done to promote the special microorganisms used to produce this style, except for temperature control during fermentation. If fermentation temperature exceeds 68oF, the Lactobacillus may produce too much acid too quickly and retard the performance of the ale yeast. The following is an example of the brewing techniques used for Berliner weisse.
- Malted Wheat 50-70%
- Light malted barley 30-50%
- No Specialty Malts
- Mash in all malts at 122°F and rest for 30 minutes.
- Heat mash to 144°F and rest for 15 minutes.
- Heat mash to 149°F and rest for 20 minutes.
- Heat mash to 162°F and rest for 15 minutes.
- Heat mash to 172°F and rest for 10 minutes.
- Sparge at 172°F until kettle is full (1.022-1.028 Specific gravity)
- Boil 60-90 minutes. Add hops (German variety such as Hallertauer or Perle) at the beginning and end of the boil to achieve 4-6 IBUs.
- Cool wort to 60°F.
- Pitch with combined culture.
- Alt or Kolsch ale yeast (Wyeast 1007 or 2565 respectively)
- Lactobacillus (Wyeast 5335)
- 5 parts yeast : 1 part bacteria
- Ferment consistently at 60° for 4-6 days.
- Prime with fresh wort (10% saved wort from the main brew) and new Lactobacillus culture. Adding more bacteria is not necessary, but will help to speed the lactic acid production.
- Store at approximately 60°F for 3-18 months (until desired lactic acid level is achieved).
- The brewing techniques similar to those of pale ales and bitters.
- A two or three step infusion mash is done using a blend of malts to yield bright orange wort.
- Styrian Golding and Hallertau-Hersbrucker hops are used throughout the boil to contribute flavor and bitterness around 33-35 IBUs.
- Belgian candy sugar is used to boost the gravity in the kettle.
- Primary fermentation is carried out with a mild Belgian strain of Saccharomyces cerevisiae.
- The beer is dry hopped in the secondary to produce a delicate spicy hop aroma.
- Brettanomyces culture in the secondary and for bottle conditioning.
- This gives the beer a very unique flavor profile.
- Beer develops flavors and aromas reminiscent of pie cherry and other Brett characters.
- The Brettanomyces culture contributes a slight tart finish
- Ferments some of the remaining complex sugars present in the beer, which gives it a high level of carbonation.
- Pale 2-Row 49%
- Pilsner malt 31%
- Munich 10L 10%
- Carapils 10%
- Crystal 60L 1%
- Mash in malts at 142°F and rest for 15 minutes.
- Heat mash to 154°F and rest for 25 minutes.
- Heat mash to 162°F and rest for 30 minutes.
- Heat mash to 170°F and rest for 10 minutes.
- Sparge at 170°F until kettle is full (1.042 specific gravity).
- Add Belgian candi sugar to increase gravity to 1.054.
- Boil for one hour, adding hops at the following times:
- At the beginning of the boil add 1 part Styrian Golding and 2 parts Hallertau-Hersbrucker to contribute ~23 IBUs.
- 30 minutes into the boil add 1 part Styrian Golding and 2 parts Hallertau-Hersbrucker to contribute ~10 IBUs.
- End of boil add Styrian Goldings for finish hops.
- Cool wort to ~63°F.
- Pitch with a mild Belgian ale strain (Wyeast 3522).
- Ferment at 65°F for 4-6 days.
- Rack to secondary.
- Add the Brettanomyces culture (Wyeast 5526)
- Add Styrian Golding whole hops.
- Condition for two weeks in secondary at cellar temperature (50°F-60°F).
- Prime with dextrose or malt extract and bottle.
- Condition at cellar temperature for 6 weeks.
- This beer can be stored for months to years, during which the hop aroma will subside and the Brett character will become more pronounced.
The brewing techniques used to brew traditional Lambics are very unique and involved. The brewing process used to produce Lambic makes use of special ingredients and steps to promote the functions of the unique microorganisms used to ferment the wort. A multiple step decoction, infusion, or both is used with grist comprised of 25-50% unmalted wheat and the remainder Pale 2-row malt and sometimes a small amount (~5%) light crystal malt. The use of unmalted wheat contributes starch and dextrins to the finished wort, which is eventually broken down by Brettanomyces sp. in the latter part of fermentation.
Wort boiling is also unique for lambic, usually lasting from three to six hours. This is done to increase the very low gravity of the wort which results from the many additions of boiling water to the mash. At the beginning of the long boil, aged oxidized hops are added. These hops are varieties out of England such as East Kent Goldings and Northern Brewer. The stale hops contribute very little bitterness to the finished beer because most of the alpha-acid has been oxidized. The main function of the hops in lambic is preservation of the beer. The aged hops tend to have a cheesy aroma, but most of this is expelled during the lengthy boil.
After the wort is boiled, it is traditionally sent to a cooling ship in an open room. Here it is naturally inoculated with the microbial flora necessary to ferment the wort. After cooling is complete the wort is sent to oak casks where it will ferment for up to two years. The following is an example of brewing techniques used to brew a lambic style beer.
- Mash in raw wheat (25-50%), 2-Row malt (50-75%), and Crystal 60L (5% if desired) at 113°F and rest for 15 minutes.
- Add 195°F water to the mash to raise the temperature to 126°F and rest for 30 minutes.
- Add 195°F water to the mash to raise the temperature to 149°F and rest for 30 minutes.
- Add 195°F water to the mash to raise the temperature to 162oF and rest for 30 minutes.
- Heat mash to 172°F and rest 15 minutes.
- Sparge at 172°F until kettle is full of ~1.036 gravity wort.
- Begin boil. Add ~0.05lb/gal of aged hops at the beginning of the boil.
- Boil for 3 hours or until a gravity of approximately 1.050.
- Cool wort to 68°F and run it into an oak barrel.
- Inoculate with Wyeast 3278 Belgian Lambic blend.
- Ferment for up to two years. During this time, the cask can be topped up with fresh wort if any volume has been lost due to evaporation.
- When the beer has reached the desired flavor profile, bottle and condition. This beer can be stored for years because of the low pH and the flavor can develop even more during this time.