Sometimes how brewers take for granted how big of an impact yeast makes on a beer. It seems like the grain bill and the hops garnish the lion share of attention, but the truth is that the yeast can play just as large of a role in certain beers. This is especially true with sours, lambics, gueuze and wild ales. One of the main yeast stains commonly used with wild ales and sours is brettanomyces or also commonly called brett.
Brettanomyces is very special because in addition to converting sugars to alcohol and CO2, it also creates a high amount of acetic acid and off flavors in certain environments. Brett or Brettanomyces is often described as adding a funky or horse blanket like flavor to beer and as you can imagine, in most cases is undesirable. It is important to note that if you are going to dabble in the use of brettanomyces or other souring bacteria such as lactobacillus and pediococcus you will want to consider setting aside specific equipment such as fermenters, kegs and racking canes for your wild ales and sours. Once these yeasts and bacteria come in contact with your fermenting equipment they can be more difficult to eradicate than typical brewing yeast strains due to their ability to survive in high temperatures, tolerate high alcohol levels and their ability to survive in low pH environments. If not, it is very important to make sure that you practice proper cleaning and sanitization methods to insure you will not contaminate future batches of beer.
Recently Brettanomyces has made become very popular in alternative beer styles. It is a powerful tool to have for a creative brewer who is working on designing interesting and flavorful beers. It is also an important reminder of just how important both yeast and fermentation conditions are in creation of a beers taste.
If you are looking to taste examples of well crafted brettanomyces beers, I highly recommend Russian River Sanctification which is a 100% brett beer and also any one of the Crooked Stave 100% brett release beers.
Vorlauf comes from the German word for mash recirculation. Vorlauf is the process of pulling the wort from the base of the mash tun or lauter tun and recirculating it back on to the top of the grain bed. Vorlauf typically occurs after the end of the mashing process. As the hot wort is recirculated through the grain bed of the mash, the grains act as a particle filter, clearing the wort. As the wort is recirculating, it becomes cleaner and less turbid until finally it is clear and ready to be passed to the boiling vessel. A pump is typically used to recirculate the wort at a steady and controlled pace. In the case where a home brewer does not have a pump available, the wort may be drawn into a container and slowly poured back on top of the grain bed. This process can be repeated until the wort has become clear. Additionally, rice hulls may be added to a mash as a means of boosting the filtration capability of the grain bed.
Wort recirculating in the mash tun prior to being transferred to the boil kettle:
Trub or hot trub is the excess material left in the boil kettle after the wort has been transferred. Boil kettle trub typically consists of hop matter, grain fiber, tannins, and the dense proteins known as the hot break that combine during the first 15 minutes of the boil, and ultimately drop to the bottom of the kettle. It is recommended that the trub not be transferred to the fermenter, as it may impart off flavors on the finished beer.
The trub that was left over in the boil kettle after the boil took place and the wort was transferred into fermenters.
Top fermentation, or top fermenting, describes the tendency of ale yeast cells to conduct the majority of fermentation on the surface of the fermentation vessel as opposed to the bottom, as is common with lager yeast. Top fermenting ale yeast is typically fermented at a temperature range between 65° F and 75° F; the lower the temperature, the slower the fermentation is carried out.
Excessive fermentation temperatures have been known to generate off flavors in beer, and that is why a temperature range of 65° F to 75° F is typically recommended. When a top fermenting ale is most active, a thick head of foam known as a krausen forms on the top of the fermentation vessel and will subside as the fermentation draws to an end. The length of fermentation is dependent on the health of the yeast, the original gravity of the wort, the temperature of the fermentation and the amount of yeast pitched, but typically takes anywhere from one week to three weeks for the majority of fermentation activity to complete. A secondary fermentation is oftentimes conducted so that any remaining fermentable sugars can be converted to alcohol, and the beer can condition and allow the yeast to precipitate to the bottom of the fermenter in preparation for bottling or kegging.
Below is a photo of a top fermenting ale that was recently transferred to a secondary fermentation carboy.
Sparging is a brewing process that involves passing heated water through the grain bed of a mash to extract sugars from the crushed grains and adjuncts. Sparging is typically conducted at approximately 167° F to 170° F; if the temperature exceeds 170° F, the brewer risks extracting excessive amounts of tannins from the grains. If the temperature is too low, then the sparge will be ineffective at liquefying the remaining converted sugars from the grains. While the sparge water passes from the hot liquor tank to the mash tun, or lauter tun, via a sparge arm, the extracted sugars and water are being drained from the base of the vessel and relocated to the boil kettle in preparation for to upcoming boil.
This mash is being sparged at 168° F, while the beer is being transferred from the false bottom at the base of the mash tun over to the boil kettle.
Sparging in the mash tun, while wort is transferred to the boil kettle.
Pitching or yeast pitching is the term used for when a brewer adds yeast to the cooled wort to begin the fermentation process. Yeast should be pitched to the wort as quickly as possible to diminish the possibility of wild yeast strains or bacteria taking control of the sweet wort before your selected yeast has the opportunity to. Additionally, your pitched yeast should be as close to the same temperature as the wort that you are adding it to in order to avoid shocking the yeast and to help the yeast acclimate as quickly as possible and lower yeast lag time. It is critical that your wort is in an appropriate temperature range for the yeast to be able to survive and thrive; for most ales that temperature range is between 65° and 80° F for pitching, but you should always consult your yeast’s packing for the specific temperature range of the variety you are using.
Cooled wort being aerated, just prior to having the yeast pitched.
Yeast pitching and aeration just prior to fermentation.
Primary fermentation in beer brewing is the initial fermentation process where yeast will convert most or all of the wort sugars to alcohol and CO2 (carbon dioxide). After the yeast has been pitched into the wort, there is typically between 2 and 24 hour yeast lag time where the yeast acclimates to the fermentation environment and begins to replicate consuming sugars and the available oxygen in the wort; there is little alcohol conversion and CO2 generated during the lag phase.
Once the lag phase completes, a foamy head called a krausen begins to form in the fermentation vessel. The krausen is composed mostly of proteins, yeast, and the carbon dioxide that the yeast is rapidly producing. During primary fermentation the yeast is producing approximately equal parts of both alcohol and CO2. Depending on the style of beer, original gravity, quantity of yeast pitched, and fermentation temperature, the primary fermentation for an ale will last between 5-14 days, then it will then be transferred to a secondary fermentation vessel to allow the beer to condition and finish out its fermentation. In some cases only a primary fermentation is completed, and the beer may spending additional time in the primary fermenter or condition in the bottle, keg, or holding vessel.
Primary fermentation occurring two days after the yeast was pitched into an American Wheat style Hefeweizen. The krausen has formed and a great deal of alcohol and CO2 is being produced.
The Reinheitsgebot, also known as the German Beer Purity Law, was originally drafted in 1487 and put into law on April 23rd, 1516 in the city of Ingolstadt, in Bavaria, Germany. The original Reinheitsgebot document stated that the only ingredients that could be used in the production of Bavarian beer were water, barley, and hops. In addition to ingredient restrictions, the document also set pricing standards for the sale of beer. At the time the Reinheitsgebot was drafted, the function of yeast in brewing was not understood, and for that reason it was not listed as an acceptable ingredient in beer.
The term noble hops refers to either German Tettnang, German Hallertauer, German Spalt or Czech Saaz hops. These noble hop varieties are all classified as aroma hops and have a relatively balanced alpha and beta acid ratio, which allows them to impart a subtle bitterness and full aroma. Each of these hops has a long tradition in brewing and is named after the region that it was originally cultivated in.
Krausen is the foamy and bubbly head that forms on top of beer during primary fermentation. As yeast ferments the sugars in a beer, it creates a great deal of CO2. The Krausen is formed as the CO2 rises to the top of the beer, mixing with proteins, yeast and residues and forming a tall layer of yeast saturated bubbles.
Krausening is also a term for when a measured amount of actively fermenting beer and/or krausen is added to a more thoroughly fermented beer as a means of conditioning or naturally carbonating the beer. Krausening is typically done as a means of carbonating a bottled beer with out violating the German beer purity laws.
Below is a video showing krausen in a 6.5 gallon carboy during primary fermentation.
Kilning is the process of drying malted grain in a kiln using an indirect heat source to halt germination and evaporate much of the moisture from the malted grains. Kilning grain started to become popular in the early 18th century and was the predominant method for drying malt by the 19th century. Prior to kilning, malt was often dried over open flame which would impart a smoke flavor in the finished beer, similar to what you may find today in a German rauchbier.
Hot break is the clumping of proteins, solids, and tannins that fall out of the wort during the boil and eventually collect at the bottom of the kettle. A steady boil is the key to achieving a good hot break, which will typically occur 5-15 minutes after the boil begins. When the foam on top of your boil finally dissipates, you know that many of the proteins have coagulated and that your hot break has occurred. A hot break is important because it aids in removing undesirable and potentially off flavor causing tannins and compounds from the boil. It also helps improve clarity and reduces the risk of chill haze down the line.
Below is a photo of the hot break in a 20 gallon brew kettle, approximately 15 minutes after the boil first began.