This article discusses the process of secondary fermentation and why it is a good thing for your beer. By employing secondary fermentation into your brewing process, you don’t need to worry about unfinished primary fermentation including the dreaded exploding bottles.
The purpose of secondary fermentation is to condition the beer. One of the key reasons to get the beer into the secondary fermenting vessel is to get it off the yeast bed. Once the initial fermentation is over, the yeast that sediments on the bottom of the primary fermenter will start to decompose. This is known as yeast autolysis and if you leave your new beer sitting on the yeast bed, it will start to adversely affect the flavor of your beer. So by racking the beer into the secondary fermenter will stop this from happening. You could of course just bottle the beer at this point but if you leave it for a secondary fermentation you give the flavors more time to mature and mellow and the improvement in the flavor of the finished beer will be considerable.
Another benefit is to avoid that “homebrew” yeasty twang. My wife reckons it tastes like marmite! This is caused by too much yeast sediment in the bottle and by allowing the secondary fermentation you will cut down on this. This is because the yeast will have consumed most of the sugars during the primary fermentation process and so you should get very little yeast sediment.
You can also use the secondary fermentation time to add many different flavorings to create your own unique beer. Some things you can do include:
Dry Hopping. This will add more aroma to the beer – just add an ounce of hops to the secondary fermenter.
Lagering. To make a proper lager you should age the beer for at least a week at a cold temperature. The garden shed in winter is a good place to keep the secondary fermenter during this process.
Clarification. There are several additives you can use to help clear your beer. The most typical are gelatin finings that can be stirred gently into the beer during secondary fermentation.
For secondary fermentation you must always use a glass or stainless steel vessel. The most commonly used vessel is a five gallon glass carboy. These are good because they have a narrow neck which only presents a very small surface area of beer when you have the stopper off and this cuts down the risk of contamination. Plastic vessels should be avoided because even if they are food grade (as in the primary fermenter), because the beer will be conditioning for extended periods you run the risk of having gases penetrating the plastic and spoiling your beer.
It is important to make sure that the initial fermentation which is usually quite vigorous has subsided. The easiest way to to do this is to count the bubbles emerging from the airlock. If they appear every thirty seconds or longer then you can proceed with racking the beer into the secondary fermenter.