I've already put in my two cents more than once in this thread but I found two pieces of information that I saved on my computer many years ago that are relevant to this old but ongoing conversation...
The first are questions from forum users (which forum I don't remember) with answers by John Palmer, author of the book How To Brew:
DON’T RACK BEER TO SECONDARY
Tom from Michigan asks:
I have a few questions about secondary fermentations. I've read both pros and cons for 2nd fermentations and it is driving me crazy what to do. One, are they necessary for lower Gravity beers?
Two, what is the dividing line between low gravity and high gravity beers? Is it 1.060 and higher?
Three, I have an American Brown Ale in the primary right now, a SG of 1.058, Should I secondary ferment this or not?
Your advice is appreciated, thanks for all you do!
Allen from New York asks:
John, please talk about why or why not you would NOT use a secondary fermenter (bright tank?) and why or why not a primary only fermentation is a good idea. In other words, give some clarification or reason whyprimary only is fine, versus the old theory of primary then secondary normal gravity ale fermentations.
Palmer answers:
These are good questions – When and why would you need to use a secondary fermenter? First some background – I used to recommend racking a beer to a secondary fermenter. My recommendation was based on the premise that (20 years ago) larger (higher gravity) beers took longer to ferment completely, and that getting the beer off the yeast reduced the risk of yeast autolysis(ie., meaty or rubbery off-flavors) and it allowed more time for flocculation and clarification, reducing the amount of yeast and trub carryover to the bottle. Twenty years ago, a homebrewed beer typically had better flavor, or perhaps less risk of off-flavors, if it was racked off the trub and clarified before bottling. Today that is not the case.
The risk inherent to any beer transfer, whether it is fermenter-to-fermenter or fermenter-to-bottles, is oxidation and staling. Any oxygen exposure after fermentation will lead to staling, and the more exposure, and the warmer the storage temperature, the faster the beer will go stale.
Racking to a secondary fermenter used to be recommended because staling was simply a fact of life – like death and taxes. But the risk of autolysis was real and worth avoiding – like cholera. In other words, you know you are going to die eventually, but death by cholera is worth avoiding.
But then modern medicine appeared, or in our case, better yeast and better yeast-handling information. Suddenly, death by autolysis is rare for a beer because of two factors: the freshness and health of the yeast being pitched has drastically improved, and proper pitching rates are better understood. The yeast no longer drop dead and burst like Mr. Creosote from Monty Python’s The Meaning of Life when fermentation is complete – they are able to hibernate and wait for the next fermentation to come around. The beer has time to clarify in the primary fermenter without generating off-flavors. With autolysis no longer a concern, staling becomes the main problem. The shelf life of a beer can be greatly enhanced by avoiding oxygen exposure and storing the beer cold (after it has had time to carbonate).
Therefore I, and Jamil and White Labs and Wyeast Labs, do not recommend racking to a secondary fermenter for ANY ale, except when conducting an actual second fermentation, such as adding fruit or souring. Racking to prevent autolysis is not necessary, and therefore the risk of oxidation is completely avoidable. Even lagers do not require racking to a second fermenter before lagering. With the right pitching rate, using fresh healthy yeast, and proper aeration of the wort prior to pitching, the fermentation of the beer will be complete within 3-8 days (bigger = longer). This time period includes the secondary or conditioning phase of fermentation when the yeast clean up acetaldehyde and diacetyl. The real purpose of lagering a beer is to use the colder temperatures to encourage the yeast to flocculate and promote the precipitation and sedimentation of microparticles and haze.
So, the new rule of thumb: don’t rack a beer to a secondary, ever, unless you are going to conduct a secondary fermentation.
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The second is a back and forth between John Palmer and Jamil Zainasheff:
DON’T RACK BEER TO SECONDARY - PART TWO
(From homebrewtalk.com in 2010!)
John: And unfortunately I'm an perpetuator of the myth at HowtoBrew.com. The 1st edition talks about the benefits of transferring the beer off the yeast.
Jamil: Well that was the popular way of doing things. But that was what, the 1st edition? Stop getting the thing off the internet. Buy yourself the 3rd addition copy and get the updated information.
John: As we've gotten more educated on how much good healthy yeast you need for optimum fermentation the advice that we used to give 20 years ago has changed. 10 years ago, 20 years ago, homebrewers were using with a single packet of dry yeast that was taped to the top of the can. There weren't as many liquid yeast cultures available.
Jamil: People didn't make starters either.
John: Right. So the whole health and vitality of yeast was different back then compared to know. Back then it made sense. You had weaker yeast that had finished fermentation that were more susceptible to autolysis and breaking down. Now that is not the case. The bar of homebrewing has risen to where we are able to make beer that has the same robustness as professional beer. We've gotten our techniques and understanding of what makes a good fermentation up to that level, so you don't need to transfer the beer off the yeast to avoid autolysis like we used to recommend.
Jamil: Unless you are going to do long term at warm temperatures, but even then we are talking over a month. I thought about this as well and I think one of the reasons autolysis....and the fact that people were using weak yeast in inappropriate amounts and the transfer would add some oxygen to it which would help attenuate a few more points. I think that was part of the deal why transferring was considered appropriate years ago.
John: But these days we don't recommend secondary transfer. Leave it in the primary, you know, a month. Today's fermentations are typically healthy enough that you are not going to get autolysis flavors or off-flavors from leaving the beer on the yeast for an extended period of time.
Jamil: And if you are using healthy yeast and the appropriate amount and the thing is... homebrew style fermenters.. if you are using a carboy or plastic bucket which have that broad base when the yeast flocculate out they lay in a nice thin layer. When you're dealing with large, tall...one of the things you know people go "Well the commercial brewers they remove the yeast because it is gonna break down, die, and make the beer bad. We should be doing the same thing." That's where a lot of this comes from. But the commercial brewers are working with 100 bbl fermenters that are very tall and puta lot of pressure on the yeast. The yeast are jammed into this little cone in the bottom and they are stacked very deep and there is a lot of heat buildup. The core of that yeast mass can be several degrees C higher than the rest of that yeast mass and it can actually cook the yeast and cause them to die faster and cause those problems with flavor and within a couple of days the viability of that yeast which the commercial brewers are going to reuse is going to drop 25%, 50% over a couple of days so they need to get that yeast out of there. You don't have that restriction as a homebrewer. You've got these broad fermenter bases that allow the yeast to be distributed evenly. It's an advantage for cleaning up the beer. You have the advantage that the yeast don't break down as fast. You don't have as high a head pressure. There are a lot of advantages.
Actually, I'm coming around. I had a Belgian quad sitting in the primary for a few months this summer. I kinda forgot about it. So far I have not noticed any ill effects but I've only had a few tastes. 