The length of time beer stays fresh in a keg depends on many key factors, including whether the keg has been opened, how the beer is dispensed, the type of beer, and the storage conditions. Usually, an unopened keg that is properly stored in a cool environment (around 3–5°C or 37–41°F) can keep its freshness for 2 to 6 months, depending on whether it is pasteurized or unpasteurized. Most commercial beers, such as those produced by big breweries, are pasteurized and can last up to six months when refrigerated. In contrast, many craft beers are unpasteurized and typically have a shorter shelf life of about six to eight weeks, even when they are stored cold.

Once a keg has been tapped, its longevity drops significantly and depends on the method used to dispense this beer. If you're using a CO₂ system, such as in a kegerator or professional bar tap setup, the beer can stay fresh for four to eight weeks after its opening. This is because CO₂ prevents oxygen from entering inside the keg, which helps preserve both carbonation and flavor. However, if a manual pump (commonly used for parties) is used, the beer is exposed to oxygen, which accelerates its spoilage. In this case, the beer should ideally be consumed within height to twelve hours.

Systems like PerfectDraft, which use sealed 6L kegs and maintain chilled, pressurized conditions, can keep beer fresh for up to 30 days after its tapping. No matter the setup, temperature control, cleanliness, and proper pressure are essential for maintaining the quality of these beers. Signs that beer has gone bad can include a flat taste, sour aroma, cloudy appearance, or a lack of foam when poured. With proper care, kegs can provide fresh beer forseveral weeks—or even months—after purchase.

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