Due to a variety of beer styles and storage options for your keg, there’s no set answer to this question. Depending on who you ask or what site you read, the answer will range between 20-120 days.
There are many variables that can play a role in how quickly your kegged beer starts to alter in taste, but a general rule to keep in mind is that as soon as that keg is filled at the brewery, the “freshness clock” starts. As time goes by, your beer will slowly start to taste less and less fresh.
How Are You Dispensing Your Beer?
To give you a better idea of how long your keg will last, let’s take a look at the two most common scenarios that one would find themselves in when they tap a keg.
1. Using a Manual Pump:
Commonly found attached to the top of kegs at house parties and backyard cookouts, the manual pump — sometimes called a bronco pump or party pump — works by pumping air into the keg, pressurizing it so that it can dispense your beer. If you’ve ever poured a beer out of a keg, then you’re probably familiar with this kind of pump, as well as the problems that come along with it, such as over-pumping and excessively foamy beer.
Unfortunately, this isn’t the only problem with the manual pump. It also drastically reduces the shelf-life of the beer inside your keg. This is because it uses oxygen to pressurize the keg. Introducing oxygen to your beer is a very bad idea, as it will quickly cause the beer to become stale and the overall flavor to rapidly change.
If you are using this kind of pump to dispense beer from a keg, then you will notice the taste of it start to change pretty quickly. This is especially true as more and more oxygen is pumped into the keg. Generally, you’ll have at least eight hours to finish the keg before the beer starts to taste stale. If you’re lucky, you may get a full day out of it before it goes completely stale. It all depends on the type of beer and how much oxygen was pumped into it.
2. Using a Kegerator with CO2
Unlike the manual pump above, a kegerator using CO2 to dispense your beer will keep it fresher for much longer. This is because the keg remains pressurized, but avoids oxidation.
In this instance, your beer can remain fresh for months, but the overall time really depends on the beer itself. If your beer is pasteurized, then it will likely last for at least three months, maybe even six if you store it at the correct temperatures. If it is not pasteurized, then it won’t last as long even if you store it at recommended temperatures. For non-pasteurized beer, you’re looking at maybe two months, give or take.
At this point, you may be asking yourself, “how do I know if it’s pasteurized or not?” This is where you would need to either contact the distributor/brewery or do some research online. If you can’t figure it out, just assume it’s non-pasteurized and treat it accordingly.
Why Storage Temperature Matters
Here’s where it starts to get a little bit more complicated: How you store your keg is important.
No matter what kind of pump you have on your keg, if you don’t store it at the right temperature you will notice a decrease in quality. The recommended temperature to store your keg is 38°F. Try not to go too much above or below that temperature.
If the temperature rises above this, your beer may become foamier as the warmer temperature liberates carbon dioxide too quickly. Not only does this cause excessive foam, but also leads to stale beer. If the temperature rises above 55°F, then it’s likely that bacteria will start to grow which will spoil the beer pretty quickly.
If you keep the temperature too cold, the beer will retain its carbonation. If this happens, you won’t be able to experience the true flavor and aroma of each pour. If the temperature falls below 28°F, then your beer will likely freeze. Obviously, you want to avoid storing it at this temperature.
It is recommended to store your keg of beer in your kegerator, or perhaps a refrigerator, so that it maintains this desired temperature at all times.
The Key to Keeping Draft Beer Fresh
The trick to keeping your keg of beer at its best is to keep oxygen out of the keg and keep it stored at the right temperature. If you can do these two things, you will have fresh draft beer for months.