Vacuum stopper and assembly of stopper and container

A vacuum stopper configured to be positioned into a neck of a container for closing the container and allowing the container to be vacuumised, the vacuum stopper comprising:

• an elongated body configured to be inserted into the neck of the container;
• a resilient shoulder provided at an upper end of the elongated body, wherein the resilient shoulder is arranged for resting onto an upper side of the neck of the container;
• a stop ring provided at the upper end of the elongated body above the resilient shoulder;
• a valve arranged inside of the elongated body for allowing, in use, air to be sucked out of the container;
• wherein the elongated body further comprises at least one radially protruding flange element,
• wherein the resilient shoulder is deformable between a rest position in which the resilient shoulder is undeformed, and a working position in which the resilient shoulder is deformed, when the stopper is positioned in the neck of the container and the inside of the container has a negative pressure, and
• wherein, in the rest position, peripheral portions of the stop ring and the resilient shoulder are separated from each other, and in the working position, the peripheral portions are collapsed together.