The Double Luck Brewing Process

The Double Luck Brewing Process:

Fermenting

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Last modified: Wed, 27 May 2009 13:22:58 -0600
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Fermenting
Fermenting

We introduce yeast, a living organism, into the wort to cause fermentation to occur. The yeast eats away at the sugars it finds, releasing large amounts of alcohol and carbon dioxide (CO₂) as "waste" materials. The alcohol, of course, will be dissolved into the liquid, while the CO₂ will be released as a gas. Before starting fermentation, we use a hydrometer to read the specific gravity of the wort and record this value for later use. This original gravity gives us an indirect measure of the amount of sugar that is available for fermentation. An alternative to a hydrometer is to use a refractometer to get a direct reading of the sugar concentration (° Brix) in the wort.

Preparing a Yeast Starter

The wort sitting in our primary fermentation vessel is an inviting target for unwanted visitors. A strong and active fermentation is the best way to protect the wort from infections from air-born bacteria and other agents. It is important to get an active fermentation going as quickly as possible. Several hours before the brewing is begun, it is common practice to prepare a yeast starter. A small amount of hopped malt extract is added to some water, boiled for a few minutes, and cooled back to room temperature. This mini-brew is placed into a sanitized vessel (this might be nothing more exotic than a glass juice jar), the yeast is added, and the vessel is closed with a fermentation lock, a device that allows CO₂ to escape, but prevents any unwanted items from entering into the vessel. By the time we have the main brew ready for the yeast, a strong and active fermentation will be present. Pitching this yeast starter onto the brew will ensure that an active fermentation in the main brew is achieved as quickly as possible.

Primary Fermentation

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The primary fermentation stage involves some vigorous activity by the yeast. This activity will produce a great deal of froth in the fermentation vessel. Because of this, it is a good idea for the primary fermentation vessel to be about 20% larger than the amount of beer we are making. It needs to large enough so that froth is not pushed through the fermentation lock, with hilarious (and messy) consequences. Primary fermentation is an aerobic process, meaning that the yeasts are using oxygen in their life cycle. For this reason, it is important that the wort contain a significant amount of dissolved oxygen before the yeast is added. At the Double Luck, we have the luxury of a stainless steel conical fermenter, large enough to accommodate a 10 gallon batch.

Secondary Fermentation

After 2 or 3 days, this initial fermentation will decrease significantly, and the yeast froth will drop back into the beer. This indicates that the secondary fermentation phase has begun. Secondary fermentation is an anaerobic process, meaning that the yeasts are not using oxygen. In fact, oxygen is now harmful to the beer, causing it to turn stale. It is important that the vessel in which secondary fermentation occurs be made from a material that is not gas permeable, so that oxygen from the atmosphere does not come in contact with the beer.

At the beginning of the secondary fermentation stage, we again use a hydrometer to read the specific gravity of the wort. This intermediate gravity gives us an indirect measure of the amount of sugar that is still available for fermentation. Alternatively, we can use a refractometer to obtain a direct reading.

At the end of the primary fermentation, copious amounts of sediment (called trub and made up mostly of dearly departed yeast cells and any particles that were not removed by the spooging process) will coat the bottom of the primary fermenter. Since this trub can cause off flavors to be produced in the beer, we want to remove as much of it as possible at this time.

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During the secondary fermentation phase, it is best to keep the beer at a relatively constant temperature. It also should not be exposed to direct sunlight. The secondary fermentation phase is much slower than the primary fermentation phase, lasting anywhere from a few days to a few weeks depending on the strength and other characteristics of the beer. When the number of gas bubbles "percolating" through the fermentation lock drops under one per minute (or less), it is time to think about moving the beer into a keg (or into bottles). A hydrometer or refractometer should be used to measure the amount of sugar remaining before moving on. There is, after all, no real rush. Assuming that the beer is safely nestled away without being exposed to oxygen or strong light, it can be left in this secondary fermentation vessel for as long as is reasonably necessary.

The stainless steel fermenter we use at the Double Luck is equipped with a butterfly valve at the bottom of the cone. This can be opened briefly to remove the trub. An alternative method, in common use where a conical fermenter is not available, is to carefully syphon the beer into a (sanitized) secondary fermentation vessel, leaving behind as much of the trub as possible. An ordinary glass carboy works well, fitted with a fermentation lock to allow CO₂ to escape.

There are a few safety precautions one should follow, as having an accident that shatters a carboy is an experience to be avoided. A strong handle should be fitted to the neck of the carboy to give positive control any time it is being moved. But this handle should not be used to lift the weight of a full carboy, since the neck is not designed for this kind of stress! Strong nylon straps forming a harness should be employed whenever a carboy full of beer is moved. Both of these items are readily available at better homebrew shops, and are a lot less expensive than a trip to the emergency room to get stitches to close the lacerations caused by flying shards of broken glass resulting from a dropped carboy striking a hard surface. Enough said.

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