A device and method for preservation of an oxidizable substance, e.g. a liquid such as a beverage of which wine is an example, is described. In a first aspect, a device is described for controlling the delivery of a predetermined amount of inert gas into a container with a single opening such as a wine bottle at a pre-determined pressure, suitable for an efficient delivery of the inert gas, with a simultaneous displacement of the air present in the top space of the container or bottle, in a simple actuation. In a second aspect, an improved container or bottle stopper is described with simple features that allow easy and cheap manufacture significantly reducing the cost of the stopper. In a third aspect to an efficient and cost-effective method is described for the preservation of a degradable substances especially liquids such as beverages of which wine is an example.