A liquid product is dispensed via a membrane contactor. The contactor employs a plurality of gas-permeable hollow fibers. The contactor has a gas port communicating with the interior of the fibers and input and output ports for liquid communicating with space within the contactor surrounding the fibers. A gas comprising carbon dioxide or nitrous oxide is dissolved in the liquid in the contactor. The gas at a controlled pressure is supplied to the gas port. The liquid is supplied at a higher pressure than the gas to the input port for liquid from a supply of such liquid via a first valve having a first valve inlet port communicating with the supply of liquid and a first valve outlet port communicating with the inlet port for liquid. Liquid with the gas dissolved therein is dispensed from the outlet port for liquid via a dispense tap to ambient. The dispensing liquid step includes a start dispense step in which dispensing commences and a stop dispense step in which dispensing is stopped. The first valve is opened with the dispensing tap in the start dispense step, and is closed in the stop dispense step. Pressure build-up is relieved in liquid in communication with the space within the contactor surrounding the fibers after closure of the first valve and while maintaining the first valve closed. The balance between gas pressure and liquid pressure during the systems' standby periods protects the membranes from flooding.