A method of making a pressurized packaged liquid beverage including filling a container including a one-way valve with a liquid mixture including a base liquid and a gum； sealing the container； introducing a volume of gas through the one-way valve after sealing the container； and agitating the container. When the container is opened, the liquid mixture increases in volume and separates into a liquid phase and a drinkable foam phase, which may persist for an extended period of time. The base liquid includes milk, coffee, fruit juice, or mixtures thereof.
