Updated April 2026.
An untapped pasteurized keg kept cold is often good 90–120 days from fill; unpasteurized draft is more like 45–60 days. That is trade guidance (Micro Matic and the same numbers used across draft suppliers), not a USDA leftover clock. The brewery’s born-on or best-by stamp on the keg is the date that matters. Once you tap with a picnic pump, you have hours, not weeks — Micro Matic says no more than 8–12 hours on air.
CO2 (or beer gas) is not air. A closed, cold, pressurized kegerator does not restart a new 120-day clock, but it also does not dump oxygen into the beer the way a party pump does.
Keg freshness windows
| Condition | Typical quality window | Why |
|---|---|---|
| Untapped, pasteurized, refrigerated | ~90–120 days from fill | Heat-treated. Many import and big-domestic kegs. |
| Untapped, unpasteurized, refrigerated | ~45–60 days from fill | Most craft draft. Treat unknown kegs as this. |
| Tapped on CO2 / beer gas, cold, clean lines | The remaining brewery window | Gas blanket, no room air. Clean lines or the beer still tastes like a hose. |
| Tapped with a picnic / party pump | 8–12 hours (Micro Matic); some retailers say up to 24 | You are pumping oxygen and microbes in. |
| Warm garage, sun, unrefrigerated | Days, then stale | Heat speeds staling. Foam and cardboard flavors first. |
The Brewers Association Draught Beer Quality Manual wants kegs stored cold (about 34–38°F) and served on gas, not compressed air. Air is for moving beer out of a half-empty party keg tonight, not for next weekend. Line cleaning is not optional if you own a kegerator.
Volume help: a full-size US half-barrel is 15.5 gallonsounces in a keg and keg cost. Fridge six-packs are a different clock: beer in the fridge.
Sour or “on purpose” mixed-fermentation kegs are a different product. If the keg was sold as a clean lager and it smells like a petri dish, dump it. Food-safety leftovers rules for cooked food are not a beer spec. Pasteurized does not mean immortal.
Sources
- Micro Matic freshness FAQ: unpasteurized ~45–60 days; pasteurized ~90–120 days on CO2 at proper temp/pressure; party pump ≤8–12 hours.
- Brewers Association Draught Beer Quality Manual: store cold; do not dispense with compressed air for quality.
- Brewery born-on / best-by on the keg is primary. Trade day-counts are not USDA.