There are a couple of important factors that will determine the success of your homebrew beer fermentation. These are the time that the yeast has to work on your wort and the temperature during fermentation.
Temperature – The temperature of your fermenting beer plays a large factor in the final result. If it is too cold the yeast will simply go to sleep (go dormant) and await a more appropriate temperature, if it is too warm though, the yeast will produce a range of strange tasting by-products that may all but ruin the flavor of your beer.
It is also particularly important to note that there are two main strains of brewing yeast. Lager yeast prefers a cooler fermenting temperature where ale yeast is happy to work at a slightly warmer temperature. In most situations the yeast included in an extract kit tin will be the more forgiving ale yeast to accommodate beginner brewers.
Time – In most cases the time listed on the side of an extract tin states that it should only need to sit in the fermenter for a week before bottling. In most cases, this is also not optimal. The goal of the companies selling extract kits is to make it seem as quick and easy as possible. As a business they are also trying to sell as much of their product as possible and less beer fermentation time means more brews.
In most cases the minimum time that you should leave your beer to ferment is about 10 days. The initial, vigorous fermentation process may be over in 4-5 days but the yeast are still happily working away. If left to do their thing, they will keep working on further improving the flavor of your beer and can be left alone for anywhere up to a month without fear.
Primary/Secondary – There are two schools of thought about the use of a secondary fermentation chamber in homebrewing. One group states that your brew should be racked off to another fermenter after about a week to move the yeast off the byproducts (aka trub) at the bottom of the fermenter to avoid any addition of off-flavors. The other idea is that given enough time, the yeast will actually start cleaning up after themselves and the trub doesn’t matter because it doesn’t make it out of the fermenter anyway.
There are those that are passionate about why either case is correct. Personally I use a process referred to as bulk priming when it comes time to bottle which moves the beer into another chamber to bottle and leaves the trub behind. I am also all about low-maintenance brewing so am all about just using a single fermentation chamber but leaving it in there for at least 2 weeks.
It is now time for you to relax and let the yeast to the hard work for a while. After about 7-10 days thoguh you will need to get invovled again in the last couple of steps in the homebrewing process. Click here for a guide on bottling your beer.