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Specific Gravity

July 18, 2013 / / 0 Comments

In brewing, specific gravity is defined as the ratio of the density of a brewing liquid, such as wort or beer, as compared to the density of pure water. Typically either a hydrometer or a refractometer is used to determine the specific gravity of beer or wort.

 
A wide selection of home brewing hydrometers and refractometers can be found here:

Hydrometers and Refractometers
Below is a photo of a hydrometer, one of the instruments used to take a specific gravity reading in brewing.

Beer Hydrometed, Final Gravity Reading

Beer Hydrometer, Final Gravity Reading

Recirculation

July 18, 2013 / / 0 Comments

Recirculation 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. Recirculation 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. The 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.

 

 

A wide selection of home brewing recirculation pumps can be found here:

Home Brewing Pumps

 

 

Wort recirculating in the mash tun, prior to sparging and transferring the wort to the boil kettle.

Wort Recirculation \ Vorlauf in the Mash Tun

Wort Recirculating in the Mash Tun

Sparging

July 18, 2013 / / 0 Comments

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.

Sparging in the mash tun, while wort is transferred to the boil kettle.

Secondary Fermentation

July 18, 2013 / / 0 Comments

Secondary fermentation is the process of transferring your beer to a secondary fermentation vessel to allow the beer to complete its fermentation cycle and condition in a clean environment. The primary reason for a secondary fermentation is to improve the taste of a beer. Towards the end of the primary fermentation, much of the yeast, beer solids, and hop solids will fall out of the beer and form sediment on the bottom of the fermenter. If left in contact with the beer too long, the dead yeast and solids can impart off or undesirable flavors upon the beer. For this reason, many brewers choose to rack the beer off of the sediment into a secondary fermenter to allow the beer to finish out fermentation, clarify, and condition.

 

The need for secondary fermentation is somewhat dependent on the style and characteristics of the beer that you are creating. For instance, if I am brewing an American wheat hefeweizen, I probably will not go through the trouble of a secondary fermentation because it is a relatively low alcohol beer with a low flocculating strain of yeast. This means it will ferment quickly, so the beer is only in contact with the sediment for a short period of time, and much of the yeast will remain in suspension with this style of beer, so a yeasty taste and cloudy appearance is appropriate.

 

If I was brewing an IPA with a high starting gravity, and I wanted to highlight the hoppy flavor of the beer, I would certainly conduct a secondary fermentation to remove as much yeast and yeast flavor from the finished beer to help both with taste and clarity. Depending on the beer style, gravity, fermentation temperatures, yeast strain, and yeast health, a secondary fermentation can typically last anywhere from two weeks to several months.  When conducting a secondary fermentation on certain beers, such as sours, the secondary fermentation can in some cases last over a year.

 

An imperial chocolate stout being racked into a secondary fermentation carboy,

Beer being racked into a Secondary Fermenter

Beer being racked into a secondary fermenter.

Primary Fermentation

July 17, 2013 / / 0 Comments

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.

Primary Fermentation

Primary Fermentation

Priming

July 17, 2013 / / 0 Comments

Priming a beer is the process of adding sugar during the bottling process in order to carbonate the beer. You can bottle condition and carbonate your beer by priming it at the time of bottling with a specific amount of sugar. Using approximately .5 teaspoons ( ½ tsp) of priming sugar per 12oz bottle will provide adequate carbonation for most beer styles.

Typically you will want to prime your beer with corn sugar (dextrose). It is critical that your beer completes its fermentation prior to priming and bottling, as residual fermentable sugars can create excessive pressure in the bottles and cause them to explode. It is also critical that the yeast is still viable so that the priming sugar is converted to CO2 in the bottle, and you do not end up with a flat and overly sweet beer. As in all aspects of brewing, cleaning and sanitation is always paramount. Take special care to ensure that your bottles and caps are clean and sanitized prior to bottling.

Racking

July 17, 2013 / / 0 Comments

Racking is the process of transferring beer from one brewing vessel to another. Beer is typically racked utilizing a racking arm, racking cane, or racking tube. The beer is either pumped from one vessel to another, or a siphon or CO2 tank is used to create a positive or negative pressure and gravity is used to rack the beer.

 

 

A wide selection of home brewing beer racking accessories can be found here:

Home Brewing Beer Racking Equipment

 

Beer being racked from a primary fermenter to a secondary fermenter using a racking cane and tube:

Beer being racked from a primary fermenter to a secondary fermenter.

Beer being racked from a primary fermenter to a secondary fermenter.

Resin

July 17, 2013 / / 0 Comments

Hop resin is a sticky compound formed in the lupulin glands of the female hop flower. The resins of the hop flower are composed of alpha and beta acids and are chiefly responsible for the bitterness and hop aroma found in beer. Additionally, alpha acids found in the hop resins function as a mild antibiotic and work as a preservative in beer.

Saccharification

July 17, 2013 / / 0 Comments

Saccharification in very basic terms is the conversion of starches to sugars. When it comes to all grain brewing, saccharification is a critical conversion process that occurs during mashing. As the mash tun’s temperature is increased to a range of 120° F to 158° F, the diastatic enzymes of the malted grains begin to activate and break the starches of the grains and adjuncts into sugars. The alpha amylase enzymes break apart complex starches into sugars that the beta amylase enzymes break apart even further into easy-to-ferment maltose sugar.

 

Precision is critical when it comes to the temperature of a mash and 10 degrees makes a massive difference. Beta amylase is more temperature dependent than alpha amylase, and when the temperature in the mash begins to rise above 158° F, the beta amylase is no longer capable of breaking apart the more complex sugar chains into maltose. So if your target mash temp is 152° F and you instead conduct your mash at 162° F, you will be left with a massive amount of unfermentable sugars in your finished beer, and it will have a fuller body and overly sweet finish.

Beta amylase thrives in a temperature range of 140° F to 150° F, so if your target mash temp was 152° F and you conducted your mash at 142° F, you would end up with a beer with a very thin body and dry finish due to a deficiency of unfermentable sugars. This is the reason why the typical mash saccharification rest temperature is in a range of 152° F to 154° F; it provides a good temperature compromise for both alpha amylase and beta amylase to carry out their required starch and sugar conversion processes.

Mouthfeel

July 16, 2013 / / 0 Comments

Mouthfeel, or the mouth feel of a beer, is the mouth’s perception of the body of a beer and is typically described as light, medium, or full. A beer’s body is formed from the residual proteins, minerals, salts’ and unfermented sugars that remain in the finished beer. The body of a beer is perceived as viscosity or thickness by the mouth. Each style of beer has a coinciding expectation for mouthfeel, and beers are rated on that expectation. For instance, a lager or pilsner should have a light body, and an imperial stout should have a full body if brewed correctly.

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.

 

 

Noble Hops

July 16, 2013 / / 0 Comments

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.

 

German Tettnang Hop, Alpha Acid 3.5-5.5%, Beta Acid 5-6%
German Hallertau Hop, Alpha Acid 3-5%, Beta Acid 4-5.5%
German Spalt Hop, Alpha Acid 4-5.5%, Beta Acid 4-5
Czech Saaz Hop, Alpha Acid 3-4.5%, Beta Acid 3-4%

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