Abstract: An oxygen absorbing cap includes a hollow chamber, a removable top that is adapted to screw into or snap into the cap so as to close the hollow chamber and, when removed, to provide access to the hollow chamber, an oxygen absorber adapted to fit into the hollow chamber, and a waterproof breathable film (e.g., e-PTFE microporous film) located in the hollow chamber between the oxygen absorber and any liquid in the bottle and adapted to prevent the liquid in the bottle from contacting the oxygen absorber but allowing gases in the bottle to contact the oxygen absorber. The cap may also be used with a valve that limits the amount of air that contacts the liquid to the air that replaces the poured liquid or used with a pump that replaces the poured liquid with oxygen-free air so that air never contacts liquid in the bottle.