The process by which an atom or molecule gains or loses electrons, acquiring a net electric charge and becoming an ion. Ionisation occurs naturally in many contexts: when salts dissolve in water, when acids release hydrogen ions, and when high-energy radiation strikes matter. In food science, the ionisation of minerals affects their solubility and bioavailability, while the ionisation state of proteins and organic acids influences flavour, colour, and texture through pH-dependent behaviour. Food irradiation works by ionising molecules in the food, disrupting the DNA of microorganisms and insects. Analytical techniques such as mass spectrometry rely on controlled ionisation to identify and quantify food components.