West Coast Brewer Home Brewing Blog

Tag: oxidization

Oxidation

Oxidation is the degradation or modification of beer when it comes in contact with oxygen or an oxidizing agent. Oxidization in beer is inevitable and occurs in beer at all times regardless of how it is stored. That being said, there are ways to diminish the rate of beer oxidation.

A good rule of thumb is to prevent oxygen from coming in contact with your beer whenever possible. The only time that oxygen should intentionally be introduced to a beer is when aerating or oxygenating wort prior to pitching yeast, and, in rare cases, to facilitate a souring process. Great caution should be taken when transferring, racking, kegging, and bottling beer to avoid splashing it or exposing it to more oxygen then is necessary.

When possible, fermentation vessels, kegs and bottles should be purged with CO2 prior to and after having beer transferred into them. Heat is another factor that impacts oxidation, and, whenever possible, beer should be stored cold to reduce oxidation rates and to preserve its freshness. Another way to help slow the impact of oxidation is to keep bottles and fermenters shielded from sunlight.

 

Beer that has been oxidized typically has a stale or paper-like taste.  In darker beers, you may also smell or taste sherry notes.

 

Autolysis

Autolysis is the destruction of a cell by the actions of its own enzymes. In brewing, autolysis typically occurs when yeast cells either decay over time or destroy each other. When the outer wall of the yeast cell is degraded and can no longer contain itself, it releases off flavors and odors into the beer. These odors are typically described as rubbery in aroma.

 

Autolysis is most common in aged beers, but can also occur in a fresh beer due to a variety of factors including unhealthy\aged yeast, stress caused by too rapid of a fermentation, excessive temperature changes and high alcohol levels. One of the best ways to reduce the impact of autolysis is to conduct a secondary fermentation as a means of removing the beer from the yeast cake. Other ways of reducing the impact of autolysis is proper aeration of the wort prior to fermentation, avoiding oxidization, keeping a consistent and appropriate fermentation temperature, and properly regulating the temperature of your finished beer.