A method of charging containers having flexible walls with a non-carbonated liquid, comprising: providing a non-carbonated liquid, dissolving a suitable gas in the non-carbonated liquid at a sub saturation level at a first temperature in a first temperature, transferring the non-carbonated liquid containing the dissolved gas into flexible walled containers to fill the containers to the top or to fill a pre-specified portion of the containers leaving an unfilled portion of the containers as a head space, closing the containers tightly, and allowing the non-carbonated liquid containing the dissolved gas to reach a second temperature whereby while maintaining a pressure in the head space to prevent deformation of the flexible walls during normal handling. The head space has a volume fraction that determines the required pressure of the dissolved gas in the non-carbonated liquid in order to produce a desired pressure build-up in the head space.