Secondary fermentation is an optional step that the homebrewer can take to further age and clarify his beer.  While the step is called secondary fermentation, not much (if any) actual fermentation takes place.  Instead, the flavor of the beer is given a chance to age and mature and any remaining bits of sediment have time to settle out of suspension.

Benefits of Secondary Fermentation

The first time you brew beer you will (understandably) probably be in a bit of a rush to try the fruits of your labor.  Unfortunately, most beers are kind of like chili and potato salad, they benefit from some time for the flavors to meld and mature.  Secondary fermentation is essentially an aging period that gives your beer the chance it needs to reach its full flavor potential.  While the yeast may not be actively converting sugars into alcohol and carbon dioxide, it is consuming some of the undesirable tastes and smells produced by the primary fermentation process.  This clean up by the yeast is known as conditioning and is very important is helping your beer taste as fresh and delicious as possible.  This aging and conditioning can be done in the bottle or the keg, but do you really think you’ll let it age once it is carbonated and ready to drink?  We don’t think so either which is why we typically like to give our beers 2-4 weeks of secondary fermentation.

We also find that our beers are extremely clear after secondary fermentation.  Most of the sediment falls to the bottom of the primary fermentation vessel during primary fermentation, so by carefully racking over to a secondary fermentation vessel you can leave all of that sediment behind while your beer ages.  The sediment that is left will typically collect and fall out of suspension leaving a very clear and bright beer.  It also stands to reason that you reduce the risk of the sediment in the primary fermentor imparting off flavors into your beer when you rack to a secondary fermentor.  If the vast majority of the sediment is gone it can’t have an effect on the quality of your beer.

Drawbacks of Secondary Fermentation

Every time you handle your beer you take the risk of it becoming contaminated by some kind of bacteria or microorganism.  At this point your beer should have a high enough of an alcohol content to protect itself from most kinds of contaminants but the risk is always still there.  The careful homebrewer can mitigate most of the risk by keeping up good cleaning and sanitation practices however.  Just like before, make sure everything that comes in contact with your beer is clean and sanitized (including the secondary fermentor) and things should go smoothly.

Another drawback is the risk of oxidizing your beer.  After the wort is aerated and the yeast is pitched, oxygen becomes one of beers mortal enemies.  When beer is exposed to oxygen its flavor begins to change and will eventually end up tasting kind of like cardboard.  Anytime you rack your beer from one vessel to another you run a high risk of introducing excess amounts of oxygen to the brew.  To help minimize this make sure that your racking equipment is long enough that the beer isn’t splashed around from one vessel to the next and take your time.  Another way to minimize oxidation is to use a 5 gallon glass carboy for your secondary fermentation vessel.  Glass will not permit oxygen exchange with the outside of the carboy and the smaller 5 gallon vessel has less headspace to hold oxygen in.  Even at this point there should be enough CO2 production to force what oxygen is in the carboy out of the fermentation lock.

Final Thoughts

Here at the Homebrew Garage we feel that putting our beers through a secondary fermentation period has helped us make consistently good beer.  We understand that there are many homebrewers who do not utilize secondary fermentation and achieve very good results.  We don’t claim to be experts; we just know what works for us.  If you are in a hurry to start enjoying your beer, by all means skip secondary fermentation.  Just do us a favor, the next time you brew that same recipe try to give it a secondary fermentation and see if you can taste the difference.