After the end of the boil and before pitching the yeast, there are a few steps required to get the wort ready for pitching:
- The wort must be cooled to a temperature low enough that it will not kill the yeast
- The wort must be transferred from the brew pot into the fermenter
- Enough oxygen must be introduced into the wort to allow for efficient fermentation
This article explains why and how each of these intermediate steps is performed.
Contents
Cooling, Racking, and Aerating for the Beginning Homebrewer
Each of these three steps can be done with expensive, specialized equipment. But for the beginning brewer, there are cheap and simple, but effective, methods for all of them, some of which are still used by many more advanced brewers. And in some cases, as the detailed sections explain, the high-tech methods may actually be less effective.
Cooling for the Beginning Homebrewer
Assuming your first batch will be a partial boil batch on your kitchen stove, with a total volume of two or three gallons, the easiest way to cool your wort is with an ice bath. When your boil ends, place the brew pot in your kitchen sink, then fill the sink around the brew pot with a mixture of crushed ice and water and leave it there until the wort is cooled to about 80 degrees Fahrenheit. You can speed the cooling by stirring gently with a sanitized spoon, being careful not to splash or agitate the wort or to do anything else that might introduce oxygen.
Some beginner books advise cooling a partial boil wort by pouring it into the additional water in the fermenter. However, this can cause oxidation of the wort and the resulting sherry or cardboardy off flavors.
Racking for the Beginning Homebrewer
Racking and siphoning is a system of transfering liquid from one vessel to another through a series of gravity-fed tubes. Essentially, it provides a way to get liquid to travel up a tube and out of one vessel, then back down and into another.
The equipment sold with most beginning brewing kits eliminates the need for racking and siphoning. Assuming your primary fermenter is a plastic bucket fermenter and you only doing a partial boil of a few gallons of wort, simply pick up your cooled wort and pour it into the fermenter bucket.
If you are using a carboy as a fermenter, you can carefully pour into a sanitized funnel. If you are doing a full wort boil, however, you will probably need to read the section on racking and siphoning below.
Aerating for the Beginning Homebrewer
While introducing oxygen to hot wort is bad, yeast needs oxygen to thrive, and your fermentation will go more smoothly if you introduce oxygen into the cooled wort before pitching the yeast.
The simplest method, and one of the most effective, is simply to shake the wort. Pick up your fermenter, put the lid on tightly, and shake it vigorously. You can do this with a partially full fermenter and then add the rest of the liquid if the full fermenter is too heavy.
Some beginning homebrew books advise you to aerate the wort simply by pouring the cooled wort into the fermenter from a height. However, wort aeration is important enough that a little bit of extra shaking would still be a good idea.
Cooling, Racking, and Aerating for the Advanced Homebrewer
Eventually, most homebrewers start doing a full-wort boil, boiling five gallons (or more) of wortin a larger brew pot. This increased wort volume requires a few extra steps, and in some cases extra equipment, to prepare the wort for pitching.
Cooling the Wort
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Cooling the wort quickly is important to avoid both oxidation or staling and infection, and five gallons or more of wort doesn't cool quickly or easily in an ice bath.
See the main article on cooling the wort for a discussion of why cooling is important and a discussion of the different types of wort chillers available to the home brewer.
Racking and Siphoning
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Various methods for transferring the wort to the fermentation vessel are used. The object here is to leave behind as much of the hot break solid material, as well as hops and any other solids. Once cooled, the wort is either poured or racked into the sanitized primary fermentation vessel. While not absolutely necessary, it is highly recommended that brewers strain their wort to some degree prior to fermentation. The hot break solids and hop debris can lend tannins and off-flavours to the beer, and it is best to remove as much of it as possible.
Typically, the cooled wort is poured, racked or pumped from the kettle into the primary fermenter. During this process, various straining methods are utilized. These include:
Whirlpooling
As the wort is cooling, it is stirred in a circular motion with a large sanitized utensil. This creates a whirlpool effect, which concentrates many of the solids in the center of the pot (where they eventually settle out), allowing for easier racking.
Hop-Back
In the hop-back method, the cooled wort is sent through a filter, such as the false bottom in the mash tun, leaving behind the hop leaves. The bed of leaves also acts as a filter for some of the other solids.
Funnel-Straining
A standard piece of equipment for homebrewing is the funnel. It is large enough to accommodate pouring, and comes equipped with a removable fine screen. With funnel straining, the wort is poured or racked into the funnel, which is placed in the neck of the primary carboy, or on the side of the primary bucket. Since the strainer tends to get clogged fairly easily, it is often a good idea to filter the wort through a larger-scale filter (such as the hop-back method) prior to sending the wort through the strainer. In all likelihood, with most beers, the brewer will also have to constantly stir the strainer (a sanitized butter knife works well) while scraping the screen in a circular motion. This continually agitates the solids on the screen, which allows liquid to pass through.
Aerating the Wort
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During the boiling process, most of the oxygen is removed from the wort liquid. Unfortunately, in order for your yeast to achieve an optimal healthy metabolic rate during fermentation (generally resulting in higher attenuation levels and a healthier overall fermentation), the brewer should introduce oxygen back into the wort prior to fermentation. While not absolutely necessary, this practice is highly recommended.
It is important that the wort be allowed to cool down to pitching temperatures prior to deliberate aeration. In order to cut down on lag time, some brewers may opt to pitch the yeast prior to aeration.
There are several methods by which aeration is accomplished:
- When doing partial-boils, unboiled (and thus, still oxygen-rich) water is added after the boil, thus introducing oxygen back into the wort. However, this alone is typically not adequate.
- When straining the wort from the kettle into the primary fermenter, the splashing and agitation that occurs introduces some oxygen back into the wort. However, this alone is typically not adequate.
- After the wort has been transferred to the primary fermenter, the brewer can seal the vessel and shake it vigorously. While this method is used alone by many brewers, it is typically less reliable and efficient than mechanical aeration/oxygenation.
See Also:
Mechanical Aeration
Most homebrew supply shops sell aeration kits specifically designed for wort aeration. They are comprised of an air pump, an in line air filter, and vinyl tubing with an aeration "stone" on the tip. Alternately, brewers may opt to build their own using fish aquarium parts. The pump is turned on, which pumps air through the lines, while the sanitized aeration "stone" is placed in cooled wort, which diffuses the oxygen and aerates the wort. 20-60 minutes is typically adequate using this method.
Mechanical Oxygenation
Similar to mechanical aeration, many homebrew supply shops sell oxygenation kits. The advantage of oxygenation kits is that the time required to introduce adequate amounts of oxygen into the wort is reduced to 15 minutes or less. The disadvantage is that these kits require the brewer to "lease" bottled O2 from a welding supply shop.
What do I do next?
Once the cool, aerated wort is in the fermenter, you are ready to move on to the next step in the beer brewing process: Preparing and Pitching Yeast.
