As an expert sommelier and brewer, I can tell you that the answer to the question of whether beer in a growler goes bad depends on a few factors. Let's dive into the details.
Firstly, it's important to note that if the growler is tightly sealed and remains unopened and chilled, the beer can stay fresh for several days. This is because the seal helps to prevent oxygen from entering the container, which is one of the main culprits behind the degradation of beer. Oxygen can oxidize the beer, causing it to develop off-flavors and spoil more quickly.
The chilling aspect is also crucial in preserving the freshness of the beer. Cold temperatures slow down the chemical reactions that lead to the degradation of the beer, helping to maintain its quality for a longer period. So, if you plan to store a growler of beer, make sure to keep it refrigerated.
However, it's worth mentioning that the type of filling system used by the bar also plays a role in the beer's freshness. Some bars employ a filling system that injects carbon dioxide (CO2) into the growler before sealing it. This additional step helps to create a protective barrier of CO2, which can further extend the beer's freshness. If you have the option, I highly recommend seeking out bars that use this type of filling system.
Now, let's move on to what happens once you open the growler. Once the seal is broken, the beer is exposed to oxygen, which starts to interact with the beer and initiate the oxidation process. This is why it's essential to consume the beer within a reasonable timeframe after opening the growler.
In my experience, an opened growler of beer can stay fresh for about 36 hours before it starts to lose its carbonation and go flat. However, this timeframe can vary depending on factors such as the style of beer, the amount of headspace left in the growler, and the temperature at which it is stored after opening.
To maximize the freshness of an opened growler, there are a few steps you can take. Firstly, be sure to seal the growler tightly after pouring the desired amount of beer. This will help minimize the beer's exposure to oxygen. Additionally, storing the open growler in the refrigerator can help slow down the oxidation process and maintain the beer's carbonation for a bit longer.
It's important to note that while the beer may go flat after a certain period, it doesn't necessarily mean it has gone bad or become undrinkable. It may still be enjoyable to consume, albeit lacking the desired effervescence.
To summarize, if the growler is tightly sealed and remains unopened and chilled, the beer can stay fresh for several days. Once opened, the beer can stay fresh for about 36 hours before it goes flat. However, the overall freshness and quality of the beer can be influenced by factors such as the type of filling system used, temperature control, and the beer style itself. So, for the best experience, aim to consume the beer as soon as possible after opening the growler.