The most common side taste I’ve encountered in my 16 years of judging experience is oxidation. Unlike other side tastes, which can be eliminated by careful washing and disinfecting, changing the yeast application rate or fermentation temperature, oxidation in beer cannot be completely eliminated – all beer becomes musty over time. The characteristics of oxidation vary greatly depending on the interaction between the other ingredients in the beer. Paper or raw cardboard are the most frequently mentioned characteristics generated by oxidation, but oxidation, particularly in stronger beers, can show up in notes of sherry or dried fruit such as prunes or apricots. Oxidation can also create a nutty flavor. Sometimes oxidation manifests itself by a weakening of flavor – the beer will seem bland or musty.
Home brewers don’t have the ability to use all the cool bottling equipment that professionals have. But there are things homebrewers can do, too, to reduce the effects of oxidation and slow down the aging process of beer. Here are some tips:
- Pour your beer fresh. When your beer is done fermenting and maturing, pour it immediately into bottles or kegs.
- Avoid splashing beer when pouring.
- Adding sugar primer just before bottling or kegging will allow the remaining yeast to use the oxygen dissolved in the beer.
- If you are doing forced carbonation in kegs, fill the keg with carbon dioxide first and, if your system allows, use CO2 to pour from the fermentation tank into the kegs. But do not use this technique with glass fermenters!
- Do not leave more than 2.5 cm of empty space when bottling.
- Most importantly, keep the bottled beer in a cool place. High temperature accelerates oxidation, so storing it cold will keep it fresh longer than storing it at room temperature.