Conditioning Kegged Beer

Bottle- and keg-conditioned ales must go through several key steps before they can be refrigerated and enjoyed. The first step is to estimate the volume of beer and to add an appropriate amount of priming sugar for carbonation. Most brewers use less sugar to prime an equivalent volume of beer in a keg compared with bottles. After the beer is primed and the container sealed, it should be transferred to a suitable environment for the carbonation or conditioning step. The normal temperatures for conditioning range from 60 to 70 °F (16–21 °C) for ale and 40 to 55 °F (4.4–13 °C) for lager.

During conditioning the yeast produce carbon dioxide from the priming sugar and also mature the beer flavor by absorbing butter-like diacetyl and green apple-esque acetaldehyde molecules and converting them into flavorless compounds. These changes are good changes and will occur in seven to 14 days in ales that are stored in the 60 to 70 °F (16–21 °C) range. Lagers will take longer and use a different procedure, but your question is about ales, so I will stick to ales!

Once the good changes brought on by conditioning have occurred there are other changes that will begin to occur that may have a negative effect on your beer’s flavor. The first bad thing to come will be yeast autolysis (yeast death and decay). Autolyzed yeast not only has an unpleasant flavor but the intracellular goo that is excreted during autolysis is rich in enzymes and nutrients. Some of the enzymes secreted, such as proteases, damage beer foam. Others, specifically esterases, change the aroma of fresh beer. As far as the nutrients released from decaying yeast cells go, they make great bacteria food. In fact many commercial breweries continually purge yeast that settles to the bottom of aging tanks. This practice is used as a preventive measure against bacterial growth.

Another change that will eventually occur in beer is oxidation. Although minimizing oxygen pick-up during beer transfers and beer packaging will reduce the rate of oxidation, oxidation is inevitable. In the early stages of oxidation, beer takes on a wet paper or wet cardboard aroma that some American imported-beer drinkers have learned to love! As the beer oxidizes more, it begins to smell like honey and eventually takes on aromas typically found in sherry and over-ripened dried fruits such as raisins and prunes. Beer drinkers fond of the rich flavors found in aged barleywines, Belgian strong ales, and the like are responding positively to oxidation, but in most beers oxidation is definitely considered a defect.

These negative changes can be delayed by minimizing the amount of yeast that is transferred into the bottle or keg, minimizing oxygen pick-up, and by using cold storage temperatures. If you store your kegs at room temperature before tapping, they may taste great for two to three weeks and begin going downhill after that period. If they are refrigerated after conditioning, they can last for months and still taste great. In a nutshell, after your been has been aged it is best to cool it for longer term storage.

Response by Ashton Lewis.