Keeping and Serving Beer
Storage and freshness
Beer is perishable. Three enemies dominate exam questions: light, oxygen, and heat. Ultraviolet and blue-spectrum light degrade iso-alpha acids into 3-methyl-2-butene-1-thiol, the compound responsible for "skunky" or lightstruck character - which is why hops are sold in light-blocking packaging and why brown glass outperforms green and clear. Oxygen drives staling (cardboard, sherry, paper), so kegs should be pushed with CO2 or beer gas, never compressed air, and bottles stored upright to minimize contact between beer and the closure. Store cool and steady; every 10 °F of warmth roughly doubles staling rate.
Draft systems
A balanced system delivers beer at the right carbonation with a clean pour. Key variables: applied pressure (must match the beer's carbonation at the serving temperature), restriction (line resistance, usually 0.25–0.30 lb per foot for 3/16" vinyl), and elevation. Typical ale lines run 5–6 feet at 10–12 psi around 38 °F. Nitro pours use 70/30 nitrogen/CO2 blends at 25–30 psi with a restrictor plate in the faucet to create the cascading, creamy head. Lines need cleaning every two weeks - beer stone and biofilm harbor lactic acid bacteria and Pediococcus.
Glassware and the pour
A "beer-clean" glass is free of grease, lipstick, and detergent residue; faults show as bubbles clinging to the side or head that collapses instantly. Match glass shape to style - tulips and snifters concentrate aroma, Willi Bechers flatter delicate lagers. Serve at style-appropriate temperature: pale lagers 38–45 °F, ales 45–52 °F, cask ale 50–55 °F, strong dark beers 55–60 °F. Trap: questions reward the idea that colder is not better; excessive chill mutes aroma and numbs the palate.
Worked example: A keg pours all foam at 12 psi and 40 °F. Rather than lowering pressure (which flattens the beer), the correct fix is to lengthen or narrow the line to add restriction and rebalance the system.