A method for measuring an amount of a determined gas, particularly oxygen, in a sealed container of a liquid, such as a carbonated beverage, in which a gas mixture is dissolved, involves piercing the sealed container, releasing the gas mixture contained in the pierced container, measuring an amount of the determined gas in the released gas mixture, determining, based on the measuring, an initial amount of the determined gas in the sealed container, and injecting an anti-foam agent into the pierced container before and/or during the gas releasing step.