A flexible and hingeable valve mechanism is provided to a package or pouch, e.g., a package top seal, creating one or more channels through the top seal of the pouch and then, approximate to the one or more channels, making or forming a pocket within the same seal. As the pocket is filled with gas, it can prevent the top seal from accidentally kinking and allow other gas pressure to flow freely through the one or more channels. If the pouch is tilted or tipped over, the pocket will fill with the liquid content of the pouch and the weight of the liquid within the pocket will cause the pocket to hingeably displace and close off at least a portion of the one or more channels to prevent leaking or spilling.