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Tag: fermentation (Page 2 of 3)

Pitching

July 17, 2013 / / 0 Comments

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

Yeast pitching and aeration just prior to fermentation.

Lag Phase

July 16, 2013 / / 0 Comments

The lag phase is the period of time in which yeast adapts to the new fermentation environment and undergoes significant reproduction.  Depending on the state of the yeast (reactivated, chilled, or dried), health of the yeast cells, variety of yeast, amount of dissolved oxygen available in the wort, temperature of the wort, and amount of available fermentable sugars, the lag phase may last anywhere from 2 to 24 hours. The lag phase begins as soon as the yeast is introduced into the wort and very little CO2 or alcohol is produced while it is active.

 

The shorter the lag time, the better, so that the desired yeast has a chance to take control of the wort before unwanted bacteria or wild yeast strains do.There are several ways to decrease your lag time, including:

  • Creating a yeast starter
  • Rehydrating dried yeast
  • Keeping your yeast and wort at the correct temperature when pitching the yeast and continuing to monitor temperature until the lag phase has ended.
  • Well-aerating your wort so that the yeast will have enough oxygen available.
  • Pitching enough yeast for the gravity of your wort.

 

 

Lager

July 14, 2013 / / 0 Comments

Lagers are beers that are fermented using a bottom fermenting yeast. These yeasts are slow fermenting and they require a lower temperature when compared to ales. Depending on the yeast strain, a lager typically conducts a primary fermentation at a temperature range between 40° F and 55° F.

Lager is the German word for storage, and lagers generally have their secondary fermentation temperature reduced and may need to condition for several months before they are considered finished.

Keg

July 13, 2013 / / 0 Comments

Kegs are cylindrical beer storage vessels that are typically constructed out of stainless steel or aluminum. They come in a variety of sizes from 2 gallons all the way up to a full size 1/2 barrel keg at 15.5 gallons.

I like to consider a keg to be a home brewer’s best friend. The primary benefit of a keg over bottles is the convenience. There is only one container to clean, sanitize, fill and carbonate; kegs are also very durable and allow you to modify your carbonation level if desired.

Most home brewers use a version of a 5 gallon keg known as a corny keg or Cornelius keg. Below is a photo of three varieties of 5 gallon kegs. On the left is a 5 gallon ball lock Cornelius keg, in the center is a 1/6th barrel keg (that you would typically receive from a large scale or craft brewery) and to the right is a pin lock conversion keg; all hold approximately 5 gallons of beer.

The ball lock kegs tend to be most common and prized by home brewers. I personally use both ball lock and pin lock kegs that have been converted to ball lock so that they are compatible with my CO2 system. I use my pin lock conversion kegs as fermentation vessels in my temperature controlled fermentation freezer. The pin lock kegs are shorter and wider which allows me to fit them in my fermentation freezer without the need of a collar extension for the freezer.

Special air locks are available for use with the keg-style fermenters; I only use them as a secondary fermenter due to the reduced head space available for the foam created during primary fermentation.

 

Below are three varieties of 5 gallon kegs.

Different Types of 5 Gallon Beer Kegs

Different types of 5 gallon beer kegs.

Ester

July 9, 2013 / / 0 Comments

An ester is chemical flavor compound that is created during the fermentation process. Ester formation is primarily dependent on the yeast strain.

In some cases, excess esters are considered an off flavor, and in other instances, it is desired—like in the case of a Bavarian hefeweizen where banana and clove tasting esters are expected. Esters are typically described as fruity, flowery, or spicy scents and flavors in a beer.

Flocculation

July 8, 2013 / / 0 Comments

Flocculation refers to a yeast strain’s tendency to clump together and drop out or fall out of suspension to the bottom of the fermenter or holding vessel. As yeast flocculates, the beer begins to clarify. Some yeast strains tend to have high flocculation, such as Wyeast Scottish – 1728, while other strains like Wyeast American Wheat – 1010 have very low flocculation. The physical appearance of the yeast cell plays a big part in its flocculation level.

It is important to choose a yeast with an appropriate flocculation profile when designing a beer; for instance you would not pair a Belgian Wit wort with a high flocculation yeast, as you want some of the yeast to stay in suspension in the finished beer.

Fermentation

July 8, 2013 / / 0 Comments

Beer fermentation is the metabolic conversion of malt and adjunct sugars to alcohol, acid, and CO2 using yeast or bacteria. As yeast and bacteria convert the wort sugars, approximately equal amounts of carbon dioxide and alcohol are produced. The alcohol being produced by the yeast is less dense than the sugars and water the yeast is metabolizing, so the gravity of the fermenting beer drops while fermentation continues to occur.

The two predominant types of fermentation are top fermenting which is used for ales, and bottom fermenting which is typical for lagers. The time frame for a fermentation to complete is dependent on a great many factors, just a few of them include the types of sugars that the wort is composed of, the amount of sugar in the wort (original gravity), the type of yeast and or bacteria used, the amount of yeast and or bacteria used, the health of the yeast and or bacteria, and temperature the fermentation occurs at. Most fermentations will take approximately two to six weeks to complete, but some may take upwards of a year before the beer is considered ready.

 

Below is a photo of beer during primary fermentation.

Primary Fermentation

Primary Fermentation

Dry Hop or Dry Hopping

July 7, 2013 / / 0 Comments

Dry hop, dry hopping, or dry hopped beer is beer that has had hops added to it during fermentation as a way of increasing hop aroma. Dry hopping is typically conducted in secondary fermentation or after primary fermentation has completed to help assure that the aroma stays in the fermenter as opposed to being pushed through the airlock with the escaping CO2.

When dry hopping, little to no bitterness is added to the fermenting beer, as the alpha acid resin is relatively insoluble in a fermenting beer at that temperature. The process of dry hopping typically lasts anywhere from a few days to a couple of weeks. Some brewers report that their beer acquires a grassy flavor if it is allowed to dry hop for more than a week or so. If grassy off flavors are a concern, you can always add additional hops for a shorter duration of time to achieve the desired dry hop aroma.

 

Dry hopping in a secondary fermentation keg. Whole hops are used in this case, but pellet or plug hops may also be used.

Dry Hop, Dry Hopping, Dry Hopped Beer in a secondary fermenter.

Dry hop, dry hopping, dry hopped beer in a secondary fermenter.

Cask Conditioning

July 6, 2013 / / 0 Comments

Cask conditioned beer refers to unfiltered and unpasteurized beer that has been conditioned in and served from a cask. This method will impart a distinctive flavor. Cask conditioned beer is naturally fermented and is typically served from the cask using a beer engine or hand-powered style pump as opposed to pushed using a CO2 tank. Cask beers tend to be served with lower levels of dissolved CO2 than one might find in a typical kegged beer. The shelf life of a casked beer is also much shorter, and the potential for oxidization is much higher since the cask walls are air permeable.

Brettanomyces – Brett

July 5, 2013 / / 0 Comments

Brett or brettanomyces is a high attenuation yeast strain that is known for the acidic, funky, wild\barnyard type tastes and smells that it produces. In most beer styles, brett it is perceived as an unwanted contaminant due to its strong and distinct flavors that can overwhelm more subtle beer flavors. Yet it is highly prized in some Belgian ales, such as gueuze, lambics, farmhouse ales, and Flanders red ales.

 

It is even used in one of my favorite Belgian Trappist beers called Orval, where their brewers add it at bottling, and allow it to ferment out and condition over time. Brettanomyces has grown in popularity over the last several years and is now used in a wide variety of styles and by many US craft breweries. When brewing with brett, it is important to avoid cross contamination with your non-brett beers as it is a robust yeast strain that can easily modify a beer’s flavor and aroma.

 

The most commonly used brett yeast strains are White Labs WLP644 Brettanomyces Bruxellensis Trois, White Labs WLP645 Brettanomyces Clausenii, White Labs WLP650 Brettanomyces Bruxellensis and Wyeast 5526 Brettanomyces Lambicus.

 

 

 

Bottom Fermenting

July 5, 2013 / / 0 Comments

Bottom fermentation or bottom fermenting is a term that describes the manner in which lager yeast tends to collect on the bottom of the fermenter and conducts its fermentation, as opposed to top fermenting ale yeast, which conducts most of its fermentation on the top of the beer.  Bottom fermenting lager yeast strains prefer a low fermentation temperature range that is typically between 40° F and 55° F, but varies between strains.

Autolysis

July 4, 2013 / / 0 Comments

Autolysis is the destruction of a cell by the actions of its own enzymes. In brewing, autolysis typically occurs when yeast cells either decay over time or destroy each other. When the outer wall of the yeast cell is degraded and can no longer contain itself, it releases off flavors and odors into the beer. These odors are typically described as rubbery in aroma.

 

Autolysis is most common in aged beers, but can also occur in a fresh beer due to a variety of factors including unhealthy\aged yeast, stress caused by too rapid of a fermentation, excessive temperature changes and high alcohol levels. One of the best ways to reduce the impact of autolysis is to conduct a secondary fermentation as a means of removing the beer from the yeast cake. Other ways of reducing the impact of autolysis is proper aeration of the wort prior to fermentation, avoiding oxidization, keeping a consistent and appropriate fermentation temperature, and properly regulating the temperature of your finished beer.

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