The Secondary Myth
Should you rack your beer to a secondary fermentor after primary fermentation is complete? When is it appropriate to rack to secondary? How long can you leave beer in a fermentor on the yeast cake before all hell breaks loose?
These questions are commonly asked, and there are people in both camps, but one of the camps is wrong. Traditional homebrewing literature posits that racking to secondary is vital if you wish to make the best possible homebrewed beer. Modern techniques and ingredients suggests that racking to secondary is a practice of the past, with an asterisk.
If you don’t want to read a bunch of text, stop after this paragraph. John Palmer, author of the seminal How to Brew, espoused the need to rack to a secondary fermentation vessel. In subsequent revisions of his book and in current conversations, he believes racking to secondary is rarely necessary (and wishes people would just buy his new revision rather than using the free first edition online to get old information). The only time racking to a secondary is advised is when actually performing a secondary fermentation (e.g. when adding fruit or souring the beer).
Quick review of racking to secondary: This is the practice of siphoning or otherwise transferring finished beer out of the primary fermentation vessel into a new one. It was done to allow the beer to condition and prevent autolysis (and its associated off-flavors) in the process. Autolysis is most likely to occur if the brewer uses unhealthy yeast or does not pitch enough yeast for the batch.
What are the risks associated with transferring to a secondary vessel? The two main risks are oxidation and infection. Oxidation can occur due to oxygen exposure during the transfer, which will cause the beer to stale sooner (as will warmer storage conditions, but that is not part of this discussion). You can mitigate oxidation by ensuring that the siphon does not get bubbles in it and that you prevent splashing during the transfer. Infection can come from a number of directions, but can be avoided with relative confidence with good sanitation practices (which you should already have), and isn’t a significant risk anyway given the alcohol content in the beer being transferred.
The alternative to racking to secondary is leaving the beer in the primary fermentor until you bottle or keg. What has changed since traditional homebrewing literature advised racking to secondary? Two main things have changed.
First, the yeast we have access to is worlds better than it used to be. There are multiple excellent sources for great yeast. In fact, it’s the same stuff that actual breweries use. Because we have access to healthy, viable yeast, we don’t have to worry much about autolysis.
The second factor is knowledge. We now know what proper pitching rates are for different gravities of wort. Since we know how much we need to pitch (and how to handle yeast), we can avoid the risk of autolysis by pitching at a proper rate (often a vial of White Labs or packet of Wyeast is enough for a standard/low gravity wort, but creating a starter is often advised for higher gravities or if you are obsessive like me).
It is now safe when utilizing healthy yeast a proper pitching rates to leave your beer on the yeast cake for several weeks, and even up to a couple of months in my experience. Leave it in your primary fermentor and it will condition properly, cleaning up acetaldehyde and diacetyl. Don’t risk oxidation and infection for no reason! This applies both to ales and lagers.
As I mentioned before, racking to secondary is sometimes necessary. However, it is only necessary when a secondary fermentation takes place. The two most common examples would be adding fruit (due to the sugars in the fruit) or souring the beer intentionally. The only other time I do it is if I want to free up my primary fermentor for a new beer.
Some of those who are firmly planted in the secondary camp also believe that the clarity of the beer is improved in a secondary vessel or that tradition is worth preserving. People who like to rack to secondary, keep doing what you’re doing. The clarity argument might be true, but I don’t feel the risk of oxidation or effort involved are worth it, and I cold crash my beer for a week before bottling anyway, which completely negates that benefit in my process.
Final words: White Labs, Wyeast, John Palmer (author of How to Brew), and Jamil Zainasheff (author of Yeast) all recommend against racking to secondary. They are all more experienced and knowledgeable than we are; listen to them.