6.) Aerate Your Wort Thoroughly
Yeast — of which you should have pitched an adequate amount — require oxygen for a healthy fermentation. Besides aerating the batch immediately before pitching, you can aerate your yeast starter several hours before pitching to help prepare the yeast. (Just pour out most of the liquid and aerate that which remains.) Or, better yet, pour a small amount of fresh, well-aerated wort (around SG 1.010–1.020) on the yeast sediment in your starter a few hours before pitching it to the main batch.
In very high gravity beers, you can even aerate after the start of fermentation. Eight to 12 hours after pitching — when fermentation has started, but before high kräusen — give the yeast a second shot of oxygen. Once the fermentation passes high kräusen, do not aerate again as this can cause your beer to have unacceptably high levels of diacetyl.
7.) Add Yeast Nutrients
A wort for a strong beer will contain all the macronutrients yeast need for a healthy fermentation. However, it may or may not have all the required micronutrients. As such, adding some yeast nutrients in the boil is a prudent thing to do. Don’t overdo it, though. More isn’t better here. Add somewhere between half and the full dose recommended by the manufacturer.
8.) Rouse the Yeast
Near the end of a difficult fermentation, you may need to rouse the yeast to finish the fermentation. If your fermentation is just shy of your target final gravity (FG), but seems to have stopped, you can stir the beer with a sanitized racking cane or something similar, or simply swirl the fermenter around a few times. This works best when the fermenting beer is at (or slightly over) the high end of the recommended temperature range. If rousing the yeast once doesn’t help, rousing it again won’t help.
Do not aerate your beer or add nutrients if your fermentation in near completion.
9.) Protect the Beer From Oxygen
Homebrewers frequently age their big beers for extended amounts of time. As beers age, any oxygen they come in contact with will promote staling. So make an effort to limit the amount of oxygen exposure your big beers receive. Do not rack your beer unless it is necessary. If you can go straight from primary to the keg or bottling bucket, do it. And rack without splashing when you do transfer the beer. Don’t open the fermenter if you don’t need to. Limit the amount of times you take samples for a hydrometer reading. (I only take readings when I’m transferring the beer. If you pitch an adequate amount of yeast, you can be fairly confident about reaching your target final gravity (FG) every time.) When bottling or kegging, work quickly to minimize the contact time with air. And if kegging, purge the headspace with CO2 after the keg is filled.
Winemakers use potassium metabisulfite (often from Campden tablets) to protect their wines from oxygen. Unofrtunately, this will not work in beer because its pH is higher than that of wine. In general, brewers don’t add anti-oxidants to their beer.
10.) Age the Beer Intelligently
Beer is a perishable product. Many homebrewers take it as written that big beers will age well over long periods of time. However, although some big beers age well, others do not. When you make a big beer, even one you intend to age for several months or even years, sample it periodically to ensure it’s still in good shape. If you have pitched an adequate amount of yeast and ran a good fermentation, your beer may mature much more quickly than you expect. Among homebrewers, you often hear that some big beers need months, if not years, to reach their peak. However, when an adequate amount of yeast is pitched initially, I’ve never found this to be the case. (Long periods of aging can clean up poorly fermented beers, but they can be over-the-hill by that point.) Even the biggest ales should be ready in a couple months if you’ve run the fermentation right. Big lagers may take a just a bit longer.
If possible, store beers you intend to age for long periods of time around 50 °F (10 °C), away from light or excessive vibration. (For other beers, the fridge is the best location.)
With these 10 tips, you should be able to manage a big beer fermentation well. I did mention pitching an adequate amount of yeast, right.