As a sommelier and brewer, I have had the opportunity to work with kegerators and kegs extensively. The freshness of beer in a kegerator can vary depending on several factors such as the beer style, the type of pump used, and the temperature at which the beer is stored.
Firstly, it's important to note that the shelf life of a keg can vary depending on whether the beer is pasteurized or not. Pasteurized beers have been treated to eliminate bacteria and yeast, which helps extend their shelf life. These beers can typically stay fresh for anywhere between 3 to 6 months when stored properly in a kegerator.
On the other hand, unpasteurized or “live” beers contain active yeast and bacteria, which continue to ferment and evolve over time. These beers are often more flavorful and complex, but they have a shorter shelf life compared to pasteurized beers. Generally, unpasteurized beers can stay fresh for up to 2 months when stored in a kegerator.
The type of pump used in the kegerator can also affect the freshness of the beer. There are two main types of pumps: air pumps and CO2 pumps. Air pumps work by using air pressure to push the beer out of the keg, while CO2 pumps use carbon dioxide to dispense the beer. CO2 pumps are generally preferred as they help maintain the carbonation and freshness of the beer for a longer period of time.
Temperature control is another crucial factor in preserving the freshness of beer in a kegerator. Ideally, the kegerator should be set to a temperature that is suitable for the specific beer style being stored. Different beer styles have different temperature requirements for optimal freshness. For example, lagers are typically stored at colder temperatures around 38-45°F (3-7°C), while ales are usually stored at slightly warmer temperatures around 45-55°F (7-13°C). By maintaining the appropriate temperature, you can help prolong the freshness of the beer in the kegerator.
In my personal experience, I have found that when all these factors are taken into consideration, kegs can indeed last for a significant amount of time in a kegerator. I have stored pasteurized beers in a kegerator for up to 6 months without any significant loss in flavor or quality. However, it's worth noting that the beer may start to lose some of its freshness and vibrancy towards the end of its shelf life.
To summarize, the shelf life of a keg in a kegerator can vary depending on the beer style, the type of pump used, and the temperature at which it is stored. Pasteurized beers can last anywhere between 3 to 6 months, while unpasteurized beers have a shorter shelf life of up to 2 months. Proper temperature control and the use of a CO2 pump can help maintain the freshness of the beer for a longer period of time.