Term for a chemical reaction in which an atom or molecule gives up electrons (oxidises) and another substance takes up these electrons (reduces). Oxidation is therefore always associated with reduction. Both processes together are partial reactions of a so-called redox reaction. Originally, oxidation was understood to be exclusively the chemical reaction of a substance with oxygen. Later, the term was expanded to include reactions in which hydrogen atoms are removed from a compound (dehydrogenation).
Oxidising agents are those substances that can easily accept electrons, such as oxygen, chlorine and fluorine. The oxidising agents are themselves reduced in the redox reaction. And reducing agents are those substances that easily give up electrons, e.g. hydrogen, carbon and base metals such as iron, magnesium and sodium. The reducing agents are oxidised during the redox reaction itself. In winemaking, oxidation should only take place in as precisely dosed and controlled a form as possible, because wine faults often occur if uncontrolled. It is, so to speak, Emperor Napoleon III. (1808-1873) that the mostly harmful influence of too much oxygen was clarified. In 1863, he commissioned the chemist Louis Pasteur (1822-1895) to investigate why so much wine spoils. The influence of microorganisms was completely unknown at that time. Pasteur discovered that too much air favours the spread of acetobacter (acetic acid bacteria), which turns wine into vinegar. But he also discovered that low oxygen exposure can positively influence the development.